Spectrometry system with visible aiming beam

ABSTRACT

A handheld spectrometer can be configured with a visible aiming beam to allow the user to determine the measured region of the object. When the visible aiming beam comprises the spectrometer measurement beam, the spectrometer measurement beam comprises sufficient energy for the user to see the measurement beam illuminating the object. When the visible aiming beam comprises a separate beam, the visible aiming beam comprises sufficient energy for the user to see a portion of the aiming beam reflected from the object. The visible aiming beam and measurement beam can be arranged to at least partially overlap on the sample, such that the user has an indication of the area of the sample being measured.

CROSS-REFERENCE

The present application is a continuation of U.S. patent applicationSer. No. 16/450,695, filed Jun. 24, 2019, entitled “SPECTROMETRY SYSTEMWITH VISIBLE AIMING BEAM”, which is a continuation of U.S. patentapplication Ser. No. 15/667,360, filed Aug. 2, 2017, entitled“SPECTROMETRY SYSTEM WITH VISIBLE AIMING BEAM”, which is a continuationof International Patent Application No. PCT/IL2016/050130, filed Feb. 4,2016, entitled “SPECTROMETRY SYSTEM WITH VISIBLE AIMING BEAM”, whichclaims the benefit of U.S. Provisional Application Ser. No. 62/112,553,filed on Feb. 5, 2015, entitled “SPECTROMETRY SYSTEM WITH VISIBLE AIMINGBEAM”, U.S. Provisional Application Ser. No. 62/154,585, filed on Apr.29, 2015, entitled “SPECTROMETRY SYSTEM WITH VISIBLE AIMING BEAM”, U.S.Provisional Application Ser. No. 62/161,728, filed on May 14, 2015,entitled “SPECTROMETRY SYSTEM WITH VISIBLE AIMING BEAM”, U.S.Provisional Application Ser. No. 62/190,524, filed on Jul. 9, 2015,entitled “SPECTROMETRY SYSTEM WITH VISIBLE AIMING BEAM”, U.S.Provisional Application Ser. No. 62/258,341, filed on Nov. 20, 2015,entitled “SPECTROMETRY SYSTEM WITH VISIBLE AIMING BEAM”, and U.S.Provisional Application Ser. No. 62/277,558, filed on Jan. 12, 2016,entitled “SPECTROMETRY SYSTEM WITH VISIBLE AIMING BEAM”, the entiredisclosures of each of which are incorporated herein by reference.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BACKGROUND OF THE INVENTION

Spectrometers are used for many purposes. For example, spectrometers areused in the detection of defects in industrial processes, satelliteimaging, and laboratory research. However, these instruments havetypically been too large and too costly for the consumer market.

Spectrometers detect radiation from a sample and process the resultingsignal to obtain and present information about the sample that includesspectral, physical and chemical information about the sample. Theseinstruments generally include some type of spectrally selective elementto separate wavelengths of radiation received from the sample, and afirst-stage optic, such as a lens, to focus or concentrate the radiationonto an imaging array.

The prior spectrometers can be less than ideal in at least somerespects. Prior spectrometers having high resolution can be larger thanideal for use in many portable applications. Although priorspectrometers with decreased size have been proposed, the priorspectrometers having decreased size and optical path length can haveless than ideal resolution, sensitivity and less accuracy than would beideal. Also, the cost of prior spectrometers can be greater than wouldbe ideal. The prior spectrometers can be somewhat bulky, difficult totransport and the optics can require more alignment than would be idealin at least some instances.

Further, data integration of prior spectrometers with measured objectscan be less than ideal in at least some instances. For example, althoughprior spectrometers can provide a spectrum of a measured object, thespectrum may be of little significance to at least some users. It wouldbe helpful if a spectrum of a measured object could be associated withattributes of the measured object that are useful to a user. Forexample, although prior spectrometers may be able to measure sugar, itwould be helpful if a spectrometer could be used to determine thesweetness of an object such as an apple. Many other examples exist wherespectral data alone does not adequately convey relevant attributes of anobject, and it would be helpful to provide attributes of an object to auser in response to measured spectral data.

Prior spectrometer methods and apparatus may have less than ideal aimingcharacteristics. Prior illumination apparatus for spectrometers may haveless specificity and accuracy than would be ideal. Further the priorspectrometer illumination devices may output more light energy thanwould be ideal. Also, in some situations it can be difficult for a userto know what area of an object is being measured.

In light of the above, an improved spectrometer and interpretation ofspectral data that overcomes at least some of the above mentioneddeficiencies of the prior spectrometers would be beneficial. Ideally,such a spectrometer would be compact, easy to aim, integrated with aconsumer device such as a cellular telephone, sufficiently rugged andlow in cost to be practical for end-user spectroscopic measurements ofitems, and convenient to use. Further, it would be helpful to providedata comprising attributes of measured objects related to the spectraldata of the objects to many people.

SUMMARY OF THE INVENTION

The present disclosure provides improved spectrometer methods andapparatus. A spectrometer may be used to determine one or more spectraof an object, and the one or more spectra may be associated with one ormore attributes of the object that are relevant to the user. While thespectrometer can take many forms, in many instances the spectrometercomprises a hand held spectrometer with wavelength multiplexing in whicha plurality of wavelengths are used to illuminate the object and measurethe one or more spectra. The handheld spectrometer can be configuredwith a visible aiming beam to allow the user to determine the measuredregion of the object. The visible aiming beam may comprise thespectrometer measurement beam, or a separate beam. When the visibleaiming beam comprises the spectrometer measurement beam, thespectrometer measurement beam comprises sufficient energy for the userto see the measurement beam illuminating the object. When the visibleaiming beam comprises a separate beam, the visible aiming beam comprisessufficient energy for the user to see a portion of the aiming beamreflected from the object. The visible aiming beam and measurement beamcan be arranged to at least partially overlap on the sample, such thatthe user has an indication of the area of the sample being measured. Thespectrometer may comprise a field of view, and the measurement beamilluminating the sample may occupy only a portion of the field of viewof the spectrometer, such that the region of the sample measured isdefined with the measurement beam. The measurement beam may overlap withthe visible aiming beam such that the visible aiming beam identifies themeasurement area of the sample for the user. This identification of thearea of the sample to be measured can help the user aim the hand heldspectrometer and provide improved measurement accuracy with decreasedartifacts. The measurement beam can be coupled to the aiming beam in oneor more of many ways with one or more of many configurations, such as acoaxial configuration in which the measurement bean and aiming beamextend coaxially together along a shared optical axis.

The spectral data of the object can be used to determine one or moreattributes of the object. In many instances, the spectrometer is coupledto a database of spectral information that can be used to determine theattributes of the object. The spectrometer system may comprise a handheld communication device coupled to a spectrometer, in which the usercan input and receive data related to the measured object with the handheld communication device. The configurations disclosed herein allowmany users to share object data with many people, in order to providemany people with actionable intelligence in response to spectral data.

In one aspect, an apparatus to measure spectra of a sample comprises adetector and a light source. The detector has a field of view to measurethe spectra of the sample within the field of view. The light source isconfigured to direct an optical beam to the sample within the field ofview, wherein a portion of the optical beam reflected from the sample isvisible to a user. The portion of the optical beam reflected from thesample visible to the user may define a measurement area of the sample.

The apparatus may further comprise a casing supported with the detectorand the light source. The detector and the light source may be arrangedto fit within the casing. The casing may be sized to fit within a handof the user, to allow the user to aim the spectrometer at the sample andmeasure the sample. The apparatus may further comprise a user inputsupported with the casing. The user input may be arranged for the userto aim the spectrometer and measure the sample with the user inputmanipulated with the hand holding the spectrometer. The apparatus mayfurther comprise circuitry coupled to the detector and the light source.The circuitry may be configured to transmit the optical beam in responseto the user input with the hand holding the hand held spectrometer.

The light source of the apparatus may be configured in order to providethe optical beam incident on the sample with an illuminance (E_(v))within a range from about 20 lux (lm/m²) to about 100,000 lux (lm/m²).The light source may be configured to provide the optical beam incidenton the sample with an irradiance within a range from about 0.1 mW/cm² toabout 100 mW/cm².

The portion of the optical beam visible to the user may comprise aportion of a measurement beam to measure the spectra of the sample. Theportion of the optical beam visible to the user may further comprise anaiming beam comprising one or more wavelengths corresponding to one ormore colors visible to the user. The one or more colors visible to theuser may comprise one or more of red, orange, yellow, blue, green,indigo or violet. The portion of the beam visible to the user maycomprise a combination of visible wavelengths of light.

The optical beam may comprise an aiming beam and a measurement beamarranged to illuminate the sample within the field of view of thedetector. The detector may comprise one or more filters to inhibittransmission of the aiming beam and to transmit the measurement beam.The one or more filters may comprise a plurality of optical filters toinhibit transmission of a portion of the aiming beam reflected from thesample and to transmit a portion of the measurement beam reflected fromthe sample. The detector may comprise a plurality of optical channels,each of the plurality of optical filters corresponding to an opticalchannel, and each optical channel comprising a field of view. The fieldof view of the detector may comprise a plurality of overlapping fieldsof view of a plurality of optical channels, wherein the aiming beam andthe measurement beam may be arranged to overlap with the plurality ofoverlapping fields of view on the object.

The apparatus may further comprise a second light source to direct ameasurement beam toward the sample, the first light source comprising anaiming beam. The measurement beam may comprise an infrared beam and theaiming beam may comprise a visible light beam.

The apparatus may further comprise one or more optics coupled to thelight source to direct the optical beam toward the sample. The one ormore optics may comprise one or more of a mirror, a beam splitter, alens, a curved reflector, or a parabolic reflector to direct the opticalbeam toward the sample. The light source may comprise a visible lightsource to generate an aiming beam and a measurement beam light source togenerate a measurement beam, wherein the one or more optics may bearranged to receive the aiming beam and the measurement beam and directthe aiming beam and the measurement beam toward the sample with theaiming beam and the measurement beam overlapping on the sample. Themeasurement beam light source may comprise a phosphorescent plate, andthe visible light source may comprise one or more of a laser diode or anLED emitting visible light energy having one or more wavelengths withina range from about 400 to 800 nm. The phosphorescent plate and the oneor more of the laser diode or the LED may be arranged coaxially in orderto transmit the measurement beam and the aiming beam along a commonoptical axis. The phosphorescent plate may be positioned to receive thevisible light energy from the one or more of the laser diode or the LED.The aiming beam may comprise a portion of the visible light energytransmitted through the phosphorescent plate, and the measurement lightbeam may comprise light energy generated with the phosphorescent plate.

The measurement beam may be configured to illuminate a measurement areaof the sample, and the aiming beam may be configured to illuminate avisible area of the sample overlapping with the measurement area, inorder to display the measurement area to the user. The visible area maycomprise from about 50% to about 150% or from about 75% to about 125% ofthe measurement area. The visible area may comprise at least about 90%,at least about 95%, or at least about 99% of of the measurement area.The one or more optics and the aiming beam and the measurement beam maybe arranged to direct the aiming beam extending along an aiming beamaxis and the measurement beam extending along a measurement beam axistoward the sample, wherein the aiming beam axis may be co-axial with themeasurement beam axis.

The detector and the light source may comprise components of aspectrometer having a volume within a range from about 1 cm³ to about200 cm³. The detector and the light source may comprise components of aspectrometer having dimensions within a range from about 0.1 cm×0.1 cm×2cm to about 5 cm×5 cm×10 cm. The detector and the light source maycomprise components of a spectrometer having a weight within a rangefrom about 1 g to about 100 g. The detector and the light source maycomprise components of a spectrometer having an optical resolution ofless than 10 nm. The light source may emit electromagnetic energycomprising one or more of ultraviolet, visible, near infrared, orinfrared light energy.

In another aspect, a method of measuring spectra of a sample comprisesproviding a detector having a field of view to measure the spectra ofthe sample within the field of view. The method further comprisesproviding a light source to direct an optical beam to the sample withinthe field of view, wherein a portion of the optical beam reflected fromthe sample is visible to a user.

The accuracy and reliability of measurements made by the spectrometermay be improved by providing a spectrometer system configured to reducethe system's sensitivity to the spatial distribution of light on thediffuser. To reduce the dependence of detected intensity distributionsof incident light on spatial variations of the light intensity on thediffuser near a diffuser plane, a filter assembly comprising a diffuserand an optical filter may be provided with the spectrometer system. Thefilter assembly may comprise two or more of an optical substrate, anoptical filter such as an interference filter, and a diffuser,integrated into a single optical component. The optical substrate can,for example, comprise a bulk visible light filter, configured to blockout wavelengths that are outside the operational range of thespectrometer. In addition to improving the accuracy and reliability ofthe spectrometer measurements, by integrating the functions of a visiblelight filter, diffuser, and/or optical filter into a single opticalcomponent, the total cost of production and the size of the spectrometercan be reduced. The filter assembly may further comprise a lens or alens array coupled directly thereto. In a spectrometer system comprisinga plurality of optical channels, the filter assembly may be coupled toan aperture array comprising a plurality of apertures having differentsizes, so as to balance the intensity of incident light transmittedthrough the filters across the different channels of the system.

The light beam may comprise a modulated light beam, and the circuitrycan be coupled to the light source and detector and configured tomeasure the sample with the modulated light beam, in order to inhibitnoise from ambient light sources. The modulated light beam may comprisevisible light, and the light beam can be modulated with frequencies awayfrom a frequency peak of the ambient light. The modulated light beam maycomprise a modulation frequency within a range from about 10 Hz to about45 Hz, or within a range from about 65 Hz to about 90 Hz, for example.Alternatively or in combination, the circuitry can be configured tomeasure the sample with one or more dark field samples and one or morepulsed samples to inhibit ambient light noise. The modulated light beamis well suited for use in combination with many spectrometers, such asspectrometers comprising a filter array or spectrometers comprising aplurality of light sources having different wavelengths, andcombinations thereof.

The spectrometer module of the compact spectrometer may comprise asupport array configured to increase the spectral range of thespectrometer. The support array can be disposed between the lens arrayand the image sensor to provide a plurality of isolated optical channelsextending from a lens of the lens array and a corresponding sensor areaof the image sensor. Each channel of the support array may be defined bya first opening facing the lens array, a second opening facing the imagesensor, and a channel wall extending therebetween. The support array maybe configured such that the channel wall extends all the way to theimage sensor, such that crosstalk between adjacent optical channels canbe inhibited, for example minimized. Inhibiting the crosstalk betweenchannels can allow the sampling of a larger portion of the image sensorwithout detecting stray light, such that the area of the image generatedon the image sensor by light from each channel can be increasedsubstantially, for example maximized. Alternatively or in combination,each channel of the support array may be configured to have around-shaped first opening facing the lens array and a rectangular orsquare-shaped opening facing the image sensor. Such a configuration canprovide rectangular or square-shaped images of light on the imagesensor. The rectangular or square-shaped images can collect additionalspectral information compared to round-shaped images. The additionalspectral information can comprise information from light having higherangles of incidence, enabling the sensor area corresponding to eachoptical channel to detect an extended spectral range of incident light.

In another aspect, an apparatus to measure spectra of a sample comprisesa filter array comprising a plurality of filters, a lens arraycomprising a plurality of lenses, an image sensor comprising a pluralityof sensor areas, and at least one diffuser. The filter array may beconfigured to receive light from the sample, the lens array configuredto receive light transmitted through the filter array, and the imagesensor configured to receive light transmitted through the lens array.The diffuser may be configured to spatially distribute the light fromthe sample substantially evenly across a front surface of the apparatus.

The at least one diffuser may comprise three or more diffusers arrangedsequentially along an optical path of the light from the sample. The atleast one diffuser may comprise a lateral diffuser configured to receiveinput light having a first lateral distribution and transmit outputlight having a second lateral distribution greater than the firstlateral distribution. The lateral diffuser may comprise a plurality ofscattering structures. The plurality of scattering structures maycomprise a refractive index that is greater than a refractive index of asupport material surround the plurality of scattering structures. Thelateral diffuser may comprise a plurality of non-overlapping scatteringstructures. The plurality of scattering structures comprises a pluralityof particles, a plurality of pores, or a combination thereof. Theplurality of scattering structures may have a size and a density perunit volume, the lateral diffuser may comprise a thickness, and thethickness of the lateral diffuser and the size and density of theplurality of scattering structures mat be arranged such that a majorityof light exiting the lateral diffuser is scattered by at least two lightscattering structures.

In another aspect, an apparatus to measure spectra of a sample comprisesa diffuser, a filter array comprising a plurality of filters, a lensarray comprising a plurality of lenses, and an image sensor comprising aplurality of sensor areas. The apparatus further comprises an aperturearray disposed between the diffuser and the lens array, and a supportarray disposed between the lens array and the image sensor. The diffusermay be configured to receive light from the sample, the filter arrayconfigured to receive light transmitted through the diffuser, the lensarray configured to receive light transmitted through the filter array,and the image sensor configured to receive light transmitted through thelens array. The aperture array may comprise a plurality of aperturesconfigured to pass light from the diffuser to the lens array, and thesupport array may comprise a plurality of channels configured to passlight from the lens array to the image sensor. The aperture array andthe support array may be collectively configured to selectively passlight from the sample incident on a front surface of the apparatus at anangle of incidence within a predetermined range.

The aperture array may comprise a first aperture array layer and asecond aperture array layer. The first aperture array layer may bedisposed between the diffuser and the filter array, and may comprise afirst plurality of apertures. The second aperture array layer may bedisposed between the filter array and the lens array, and comprise asecond plurality of apertures aligned with the first plurality ofapertures. The first and second aperture layers may be arranged to blocklight having an angle of incidence outside the predetermined range frompassing through to the lens array.

Each of the first plurality of apertures may have a first diameter, eachof the second plurality of apertures may have a second diameter, and thefirst aperture layer array and the second aperture array layer may beseparated by a separation distance. One or more of the first diameter,the second diameter, and the separation distance may be arranged toblock light have the angle of incident outside the predetermined range.The first diameter may be greater than the second diameter, the seconddiameter may be greater than the first diameter, or the first diameterand the second diameter may be equal.

The filter array may comprise an opaque material disposed betweenadjacent filters of the plurality of filters. The opaque material may beconfigured to prevent cross-talk of light between the adjacent filters.

A side wall of each of the plurality of channels of the support arraymay be configured to reduce an intensity of light by at least about 90%after a single reflection of the light from the side wall. Each of theplurality of channels of the support array may be shaped substantiallyas a frustum, wherein a top opening of the channel is smaller than abottom opening of the channel. Each channel may comprise a continuous,rounded side wall, or each channel may comprise two or more side wallsconnected at an angle relative to one another. Each channel may comprisethree or more straight side walls connected at one or more anglesrelative to one another, such that a horizontal cross-section of thechannel forms a polygon. The two or more side walls may be arranged suchthat light entering the channel is reflected from the two or more sidewalls at least two times before exiting the channel. A side wall of eachof the plurality of channels of the support array may be configured toprovide substantially specular reflection of light from the side wall,or substantially diffusive reflection of light from the side wall.

Each of the plurality of channels of the support array may comprise oneor more side walls extending from a top end of the channel to a bottomend of the channel, and a bottom wall extending over the bottom end. Thebottom wall may comprise a central opening therethrough, wherein an areaof the central opening is smaller than a cross-sectional area of thechannel at the bottom end. The one or more side walls and the bottomwall may be arranged to selectively allow the light having the angle ofincidence within the predetermined range to pass through the centralopening and exit the channel.

The apparatus may further comprise an angle limiting layer disposedbetween the diffuser and the filter array, wherein the angle limitinglayer is configured to selectively allow the light having the angle ofincidence within the predetermined range to pass therethrough. The anglelimiting layer may comprise a micro-louver film having a plurality oflight transmissive sections and a plurality of light blocking sectionsarranged alternatingly along a length of the micro-louver film. One ormore of a thickness of the micro-louver film and a distance betweenadjacent light blocking sections may be configured to selectively allowsthe light having the angle of incidence within the predetermined rangeto pass through to the filter array. The angle limiting layer maycomprises a prism film having an input surface configured to receivelight and an output surface configured to output the light, the outputsurface comprising a plurality of microstructures configured to modifyan angle of transmission of the output light. The plurality ofmicrostructures may be configured to output light selectively comprisingthe light having the angle of incidence within the predetermined range.The plurality of microstructures may be further configured to redirectlight having an angle of incidence greater than a predeterminedthreshold value to adjacent microstructures or back towards thediffuser. The plurality of microstructures may comprise a plurality ofpyramid shaped structures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show an isometric view of a compact spectrometer, inaccordance with configurations.

FIG. 2 shows a schematic diagram of a spectrometer system, in accordancewith configurations.

FIG. 3 shows a schematic diagram of the compact spectrometer of FIGS. 1Aand 1B, in accordance with configurations.

FIG. 4 shows a schematic diagram of an optical layout in accordance withconfigurations.

FIG. 5 shows a schematic diagram of a spectrometer head, in accordancewith configurations.

FIG. 6 shows a schematic drawing of cross-section A of the spectrometerhead of FIG. 5 , in accordance with configurations.

FIG. 7 shows a schematic drawing of cross-section B of the spectrometerhead of FIG. 5 , in accordance with configurations.

FIG. 8 shows an isometric view of a spectrometer module in accordancewith configurations.

FIG. 9 shows the lens array within the spectrometer module, inaccordance with configurations.

FIG. 10 shows a schematic diagram of an alternative embodiment of thespectrometer head, in accordance with configurations.

FIG. 11 shows a schematic diagram of an alternative embodiment of thespectrometer head, in accordance with configurations.

FIG. 12 shows a schematic diagram of a cross-section of the spectrometerhead of FIG. 11 .

FIG. 13 shows an array of LEDs of the spectrometer head of FIG. 11arranged in rows and columns, in accordance with configurations.

FIG. 14 shows a schematic diagram of a radiation diffusion unit of thespectrometer head of FIG. 11 , in accordance with configurations.

FIGS. 15A and 15B show examples of design options for the radiationdiffusion unit of FIG. 13 , in accordance with configurations.

FIGS. 16A and 16B are schematic drawings of cross-sectional views of anoptical subassembly of a spectrometer module, in accordance withconfigurations.

FIG. 17 is a schematic drawing of a portion of an optical subassembly ofa spectrometer module, in accordance with configurations.

FIG. 18 shows a schematic diagram of an optical layout in accordancewith configurations.

FIGS. 19A-19F illustrate exemplary configurations of a filter assemblysuitable for incorporation with a compact spectrometer.

FIG. 20 shows a schematic drawing of a cross-section of an exemplaryspectrometer module, comprising an array of filter assemblies.

FIG. 21 shows an example of a noise spectrum.

FIG. 22 shows an exemplary method of measuring a spectrum.

FIG. 23 schematically illustrates the crosstalk between channels of asensor array.

FIG. 24A shows a cross-sectional view of an optical subassemblycomprising an exemplary support array.

FIG. 24B schematically illustrates the light pattern detected by theimage sensor for the support array configuration of FIG. 24A.

FIGS. 25A-25C illustrate an exemplary embodiment of a support arraycomprising channels having square-shaped openings facing the imagesensor.

FIG. 25D schematically illustrates the light pattern detected by theimage sensor for the support array configuration of FIGS. 25A-C.

FIG. 26 shows an oblique view of an exemplary optical module assembly ofa compact spectrometer.

FIGS. 27A and 27B schematically illustrate the lateral distribution oflight transmitted through one or more cosine diffusers.

FIG. 27C illustrates an exemplary configuration of a lateral diffuser.

FIG. 28 illustrates an exemplary configuration of an optical stack of afilter array-based spectrometer, and the passage of stray light throughthe optical stack to the detector.

FIG. 29A illustrates an optical stack comprising two aperture arraylayers and an opaque material disposed between adjacent filters of thefilter array.

FIG. 29B schematically illustrates the passage of light through thefirst and second aperture array layers of FIG. 29A.

FIG. 30A illustrates an exemplary configuration of a channel of asupport array.

FIGS. 30B and 30C illustrate horizontal cross-sections of exemplaryconfigurations of the channel of FIG. 30A.

FIG. 31 illustrates a configuration of a support array channelcomprising a bottom wall having a central opening.

FIG. 32A illustrates an exemplary configuration of an optical stackcomprising an angle limiting layer.

FIG. 32B schematically illustrates an exemplary angle limiting layercomprising a micro-louver film.

FIG. 32C schematically illustrates another exemplary angle limitinglayer comprising a prism film.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, various aspects of the invention will bedescribed. For the purposes of explanation, specific details are setforth in order to provide a thorough understanding of the invention. Itwill be apparent to one skilled in the art that there are otherembodiments of the invention that differ in details without affectingthe essential nature thereof. Therefore the invention is not limited bythat which is illustrated in the figure and described in thespecification, but only as indicated in the accompanying claims, withthe proper scope determined only by the broadest interpretation of saidclaims.

A better understanding of the features and advantages of the presentdisclosure will be obtained by reference to the following detaileddescription that sets forth illustrative embodiments, in which theprinciples of embodiments of the present disclosure are utilized, andthe accompanying drawings.

The configurations disclosed herein can be combined in one or more ofmany ways to provide improved spectrometer methods and apparatus. One ormore components of the configurations disclosed herein can be combinedwith each other in many ways. A spectrometer as described herein can beused to generate spectral data of the object, and the spectral data ofthe object transmitted to a cloud based server in order to determine oneor more attributes of the object. Alternatively or in combination, dataof the cloud based server can be made available to both users andnon-users of the spectrometers in order to provide useful informationrelated to attributes of measured objects. The data of the cloud basedserver can be made available to users and non-users in many ways, forexample with downloadable apps capable of connecting to the cloud basedserver and downloading information related to spectra of many objects.

The configurations disclosed herein are also capable of providing adatabase of attributes of many objects related to spectral data. Amobile communication device can be configured for a user to inputattributes of one or more measured objects in order to construct adatabase based on spectral data of many measured objects.

As used herein, like characters refer to like elements. As used herein,the term “light” encompasses electromagnetic radiation havingwavelengths in one or more of the ultraviolet, visible, or infraredportions of the electromagnetic spectrum. As used herein, the term“dispersive” is used, with respect to optical components, to describe acomponent that is designed to separate spatially, the differentwavelength components of a polychromatic beam of light. Non-limitingexamples of “dispersive” optical elements by this definition includediffraction gratings and prisms. The term specifically excludes elementssuch as lenses that disperse light because of non-idealities such aschromatic aberration or elements such as interference filters that havedifferent transmission profiles according to the angle of incidentradiation. The term also excludes the filters and filter matrixesdescribed herein. As used herein, the term “store” encompasses astructure that stores objects, such as a crate or building.

The dimensions of an optical beam as described herein can be determinedin one or more of many ways. The size of the beam may comprise a fullwidth half maximum of the beam, for example. The measurement beam maycomprise blurred edges, and the measurement area of the beam definingthe measurement area of the sample may comprise a portion of the beamextending beyond the full width half maximum of the beam, for example.The dimensions of the aiming beam can be similarly determined.

Overview of Compact Spectrometer System

FIGS. 1A and 1B show an isometric view of a compact spectrometer 102, inaccordance with configurations. The spectrometer 102 can be used as ageneral purpose material analyzer for many applications, as described infurther detail herein. In particular, the spectrometer 102 can be usedto identify materials or objects, provide information regarding certainproperties of the identified materials, and accordingly provide userswith actionable insights regarding the identified materials. Thespectrometer 102 comprises a spectrometer head 120 configured to bedirected towards a sample material S. The spectrometer head 120comprises a spectrometer module 160, configured to obtain spectralinformation associated with the sample material S. The spectrometer head120 may also comprise a sensor module 130, which may, for example,comprise a temperature sensor. The spectrometer may comprise simplemeans for users to control the operation of the spectrometer, such asoperating button 1006. The compact size of the spectrometer 102 canprovide a hand held device that can be directed (e.g., pointed) at amaterial to rapidly obtain information about the material. For example,as shown in FIGS. 1A and 1B, the spectrometer 102 may be sized to fitinside the hand H of a user.

FIG. 2 shows a schematic diagram of a spectrometer system, in accordancewith configurations. In many instances, the spectrometer system 100comprises a spectrometer 102 as described herein and a hand held device110 in wireless communication 116 with a cloud based server or storagesystem 118. The spectrometer 102 can acquire the data as describedherein. The hand held spectrometer 102 may comprise a processor 106 andcommunication circuitry 104 coupled to the spectrometer head 120 havingspectrometer components as described herein. The spectrometer cantransmit the data to the hand held device 110 with communicationcircuitry 104 with a communication link, such as a wireless serialcommunication link, for example Bluetooth™ The hand held device canreceive the data from the spectrometer 102 and transmit the data to thecloud based storage system 118. The data can be processed and analyzedby the cloud based server 118, and transmitted back to the hand helddevice 110 to be displayed to the user. In addition, the analyzedspectral data and/or related additional analysis results may bedynamically added to a universal database operated by the cloud server118, where spectral data associated with sample materials may be stored.The spectral data stored on the database may comprise data generated byone or more users of the spectrometer system 100, and/or pre-loadedspectral data of materials with known spectra. The cloud server maycomprise a memory having the database stored thereon.

The spectrometer system may allow multiple users to connect to the cloudbased server 118 via their hand held devices 110, as described infurther detail herein. In some instances, the server 118 may beconfigured to simultaneously communicate with up to millions of handheld devices 110. The ability of the system to support a large number ofusers and devices at the same time can allow users of the system toaccess, in some instances in real-time, large amounts of informationrelating to a material of interest. Access to such information mayprovide users with a way of making informed decisions relating to amaterial of interest.

The hand held device 110 may comprise one or more components of a smartphone, such as a display 112, an interface 114, a processor, a computerreadable memory and communication circuitry. The device 110 may comprisea substantially stationary device when used, such as a wirelesscommunication gateway, for example.

The processor 106 may comprise a tangible medium embodying instructions,such as a computer readable memory embodying instructions of a computerprogram. Alternatively or in combination the processor may compriselogic such as gate array logic in order to perform one or more logicsteps.

FIG. 3 shows a schematic diagram of a compact spectrometer of FIGS. 1Aand 1B. The spectrometer 102 may comprise a spectrometer head 120 and acontrol board 105. The spectrometer head 120 may comprise one or more ofa spectrometer module 160 and an illumination module 140, which togethercan be configured to measure spectroscopic information relating to asample material as described in further detail herein. The spectrometerhead 120 may further comprise one or more of a sensor module 130, whichcan be configured to measure non-spectroscopic information relating to asample material, such as ambient temperature. The control board 105 maycomprise one or more of a processor 106, communication circuitry 104,and memory 107. Components of the control board 105 can be configured totransmit, store, and/or analyze data, as described in further detailherein.

The sensor module 130 can enable the identification of the samplematerial based on non-spectroscopic information in addition to thespectroscopic information measured by the spectrometer module 160. Sucha dual information system may enhance the accuracy of detection oridentification of the material.

The sensor element of sensor module 130 may comprise any sensorconfigured to generate a non-spectroscopic signal associated with atleast one aspect of the environment, including the material beinganalyzed. For example, the sensor element may comprise one or more of acamera, temperature sensor, electrical sensor (capacitance, resistance,conductivity, inductance), altimeter, GPS unit, turbidity sensor, pHsensor, accelerometer, vibration sensor, biometric sensor, chemicalsensor, color sensor, clock, ambient light sensor, microphone,penetrometer, durometer, barcode reader, flowmeter, speedometer,magnetometer, and another spectrometer.

The output of the sensor module 130 may be associated with the output ofthe spectrometer module 160 via at least one processing device of thespectrometer system. The processing device may be configured to receivethe outputs of the spectrometer module and sensor module, analyze bothoutputs, and based on the analysis provide information relating to atleast one characteristic of the material to a display unit. A displayunit may be provided on the device in order to allow display of suchinformation.

The spectrometer module 160 may comprise one or more lens elements. Eachlens can be made of two surfaces, and each surface may be an asphericsurface. In designing the lens for a fixed-focus system, it may bedesirable to reduce the system's sensitivity to the exact location ofthe optical detector on the z-axis (the axis perpendicular to the planeof the optical detector), in order to tolerate larger variations anderrors in mechanical manufacturing. To do so, the point-spread-function(PSF) size and shape at the nominal position may be traded off with thedepth-of-field (DoF) length. For example, a larger-than-optimal PSF sizemay be chosen in return for an increase in the DoF length. One or moreof the aspheric lens surfaces of each lens of a plurality of lenses canbe shaped to provide the increased PSF size and the increased DoF lengthfor each lens. Such a design may help reduce the cost of production byenabling the use of mass production tools, since mass production toolsmay not be able to meet stringent tolerance requirements associated withsystems that are comparatively more sensitive to exact location of theoptical detector.

In some cases, the measurement of the sample may be performed usingscattered ambient light. In some cases, the spectrometer system maycomprise a light or illumination source, such as illumination module140. The light source can be of any type (e.g., laser, light-emittingdiode, etc.) known in the art appropriate for the spectral measurementsto be made. The light source may emit from 350 nm to 1100 nm. The lightsource may emit from 0.1 mW to 500 mW. The wavelength(s) and intensityof the light source can depend on the particular use to which thespectrometer will be put.

The spectrometer may also include a power source, such as a battery orpower supply. In some instances the spectrometer is powered by a powersupply from a consumer hand held device (e.g. a cell phone). In someinstances the spectrometer has an independent power supply. In someinstances a power supply from the spectrometer can supply power to aconsumer hand held device.

The spectrometer as described herein can be adapted, with proper choiceof light source, detector, and associated optics, for a use with a widevariety of spectroscopic techniques. Non-limiting examples includeRaman, fluorescence, and IR or UV-VIS reflectance and absorbancespectroscopies. Because, as described herein, a compact spectrometersystem can separate a Raman signal from a fluorescence signal, the samespectrometer may be used for both spectroscopies. The spectrometer maynot comprise a monochromator.

Referring again to FIGS. 1A and 1B, a user may initiate a measurement ofa sample material S using the spectrometer 102 by interacting with auser input supported with a casing or container 902 of the spectrometer.The user input may, for example, comprise an operating button 1006. Thecasing or container 902 may be sized to fit within a hand H of a user,allowing the user to hold and aim the spectrometer at the samplematerial, and manipulate the user input with the same hand H to initiatemeasurement of the sample material. The casing or container 902 canhouse the different parts of the spectrometer such as the spectrometermodule 160, illumination module 140, and sensor module 130. Thespectrometer module may comprise a detector or sensor to measure thespectra of the sample material within a field of view 40 of thedetector. The detector may be configured to have a wide field of view.The illumination module may comprise a light source configured to directan optical beam 10 to the sample material S within the field of view 40.The light source may be configured to emit electromagnetic energy,comprising one or more of ultraviolet, visible, near infrared, orinfrared light energy. The light source may comprise one or morecomponent light sources. The illumination module may further compriseone or more optics coupled to the light source to direct the opticalbeam 10 toward the sample material S. The one or more optics maycomprise one or more of a mirror, a beam splitter, a lens, a curvedreflector, parabolic reflector, or parabolic concentrator, as describedin further detail herein. The spectrometer 102 may further comprise acircuitry coupled to the detector and the light source, wherein thecircuitry is configured to transmit the optical beam 10 in response touser interactions with the user input using hand H holding thespectrometer.

When a user initiates a measurement of a sample material S using thespectrometer 102, for example by pressing the operating button 1006 withhand H, the spectrometer emits an optical beam 10 toward the samplematerial within the field of view 40. When the optical beam 10 hits thesample material S, the light may be partially absorbed and/or partiallyreflected by the sample material; alternatively or in combination,optical beam 10 may cause the sample material to emit light in response.The detector of the spectrometer module 160 may be configured to senseat least a portion of the optical beam 10 reflected back by the sampleand/or light emitted by the sample in response to the optical beam 10,and consequently generate the spectral data of the sample material asdescribed in further detail herein.

The spectrometer 102 may be configured to begin measurement of a samplematerial S with just ambient light, without the optical beam 10. Aftercompleting the measurement with ambient light only, the illuminationmodule 140 of the spectrometer 102 can generate the optical beam 10, andthe spectrometer module 160 can begin measurement of the sample materialwith the optical beam 10. In this case, there may be a brief time lapsebetween the initiation of a measurement, for example by a user pressingthe operating button 1006, and the generation of the optical beam 10 andthe visible portions thereof. The ambient light-only measurement can beused to reduce or eliminate the contribution of ambient light in thespectral data of the sample material S. For example, the measurementmade with ambient light only can be subtracted from the measurement madewith the optical beam 10.

A portion of the optical beam 10 that is reflected from the samplematerial S may be visible to the user; this visible, reflected portionof optical beam 10 may define the measurement area 50 of the samplematerial S. The measurement area 50 of the sample may at least partiallyoverlap with and fall within the field of view 40 of the detector of thespectrometer. The area covered by the field of view 40 may be largerthan the visible area of the sample illuminated by the optical beam 10,or the measurement area 50 defined by the visible portion of the opticalbeam 10. Alternatively, the field of view may be smaller than theoptical beam, for example. In many configurations, the field of view 40of the detector of the spectrometer module is larger than the areailluminated by the optical beam 10, and hence the measurement area 50 isdefined by the optical beam 10 rather than by the field of view 40 ofthe detector.

The visible portion of optical beam 10 may comprise one or morewavelengths corresponding to one or more colors visible to the user. Forexample, the visible portion of optical beam 10 may comprise one or morewavelengths corresponding to the colors red, orange, yellow, blue,green, indigo, violet, or a combination thereof. The visible portion ofoptical beam 10 reflected from the sample material S may comprise about0.1% to about 10%, about 1% to about 4%, or about 2% to about 3% ofoptical beam 10. The visible portion of optical beam 10 may compriselight operating with power in a range from about 0.1 mW to about 100 mW,about 1 mW to about 75 mW, about 1 mW to about 50 mW, about 5 mW toabout 40 mW, about 5 mW to about 30 mW, about 5 mW to about 20 mW, orabout 10 mW to about 15 mW. The visible portion of optical beam 10incident on the sample may have an intensity in a range from about 0.1mW to about 100 mW, about 1 mW to about 75 mW, about 1 mW to about 50mW, about 5 mW to about 40 mW, about 5 mW to about 30 mW, about 5 mW toabout 20 mW, or about 10 mW to about 15 mW. The visible portion ofoptical beam 10 incident on the sample may have an intensity or totallight output in a range from about 0.001 lumens to about 10 lumens,about 0.001 lumens to about 5 lumens, about 0.005 lumens to about 10lumens, about 0.01 lumens to about 10 lumens, about 0.005 lumens toabout 5 lumens, about 0.05 lumens to about 5 lumens, about 0.1 lumens toabout 5 lumens, about 0.2 lumens to about 1 lumens, or about 0.5 lumensto about 5 lumens.

The optical beam 10 incident on the sample S may have an area of about0.5 to about 2 cm², or about 1 cm². Accordingly, the optical beam 10incident on the sample S may have an irradiance within a range fromabout 0.1 mW/cm² to about 100 mW/cm², about 1 mW/cm² to about 75 mW/cm²,about 1 mW/cm² to about 50 mW/cm², about 5 mW/cm² to about 40 mW/cm²,about 5 mW/cm² to about 30 mW/cm², about 5 mW/cm² to about 20 mW/cm², orabout 10 mW/cm² to about 15 mW/cm². The optical beam 10 incident on thesample S may have an illuminance (E_(v)) within a range from about 20lux (lumens/m²) to about 100,000 lux, about 200 lux to about 75,000 lux,about 400 lux to about 50,000 lux, about 2,000 lux to about 25,000 lux,about 2,000 lux to about 15,000 lux, about 4,000 lux to about 15,000lux, or about 4,000 lux to about 6,000 lux.

The light output of the visible portion of optical beam 10 may varydepending on the type of light source. In some cases, the visible lightoutput of optical beam 10 may vary due to the different luminousefficacies of different types of light source. For example, bluelight-emitting diode (LED) may have an efficacy of about 40 lumens/W, ared LED may have an efficacy of about 70 lumens/W, and a green LED mayhave an efficacy of about 90 lumens/W. Accordingly, the visible lightoutput of optical beam 10 may vary depending on the color or wavelengthrange of the light source.

The light output of the visible portion of optical beam 10 may also varydue to the nature of interactions between the different components of alight source. For example, the light source may comprise a light sourcecombined with an optical element configured to shift the wavelength ofthe light produced by the first light source, as described in furtherdetail herein. In this embodiment, the visible light output of thevisible portion of optical beam 10 may vary depending on the amount ofthe light produced by the light source that is configured to passthrough the optical element without being absorbed orwavelength-shifted, as described in further detail herein.

As shown in FIG. 1A, the optical beam 10 may comprise a visible aimingbeam 20. The aiming beam 20 may comprise one or more wavelengthscorresponding to one or more colors visible to the user, such as red,orange, yellow, blue, green, indigo, or violet. Alternatively or incombination, the optical beam 10 may comprise a measurement beam 30,configured to measure the spectra of the sample material. Themeasurement beam 30 may be visible, such that the measurement beam 30comprises and functions as a visible aiming beam. As shown in FIG. 1B,the optical beam 10 may comprise a visible measurement beam 30 thatcomprises a visible aiming beam. The measurement beam 30 may compriselight in the visible spectrum, non-visible spectrum, or a combinationthereof. The aiming beam 20 and the measurement beam 30 may be producedby the same light source or by different light sources within theillumination module 140, and can be arranged to illuminate the samplematerial S within the field of view 40 of the detector or sensor of thespectrometer 102. The visible aiming beam 20 and the optical beam 30 maybe partially or completely overlapping, aligned, and/or coaxial.

The visible aiming beam 20 may comprise light in the visible spectrum,for example in a range from about 390 nm to about 800 nm, which the usercan see reflected on a portion of the sample material S. The aiming beam20 can provide basic visual verification that the spectrometer 102 isoperational, and can provide visual indication to the user that ameasurement is in progress. The aiming beam 20 can help the uservisualize the area of the sample material being measured, and therebyprovide guidance the user in adjusting the position and/or angle of thespectrometer 102 to position the measurement area 50 over the desiredarea of the sample material S. The aiming beam 20 may be configured withcircuitry to be emitted throughout the duration of a measurement, andautomatically turn off when the measurement of the sample material S iscomplete; in this case, the aiming beam 20 can also provide visualindication to the user of how long the user should hold the spectrometer102 pointed at the sample material S.

The visible aiming beam 20 and the measurement beam 30 may be producedby the same light source, wherein the visible aiming beam 20 comprises aportion of the measurement beam 30. Alternatively, the aiming beam 20may be produced by a first light source, and the measurement beam 30 maybe produced by a second light source. For example, the measurement beam30 may comprise an infrared beam and the aiming beam 20 may comprise avisible light beam.

The measurement beam 30 may be configured to illuminate the measurementarea 50 of the sample S, and the aiming beam 20 may be configured toilluminate an area of the sample overlapping with the measurement area,thereby displaying the measurement area to the user. The visible areailluminated by the visible aiming beam 20 may comprise from about 50% toabout 150% or about 75% to about 125% of the measurement area, or atleast about 90%, at least about 95%, or at least about 99% of themeasurement area.

One or more optics of the illumination module, such as a lens or aparabolic reflector, may be arranged to receive the aiming beam 20 andthe measurement beam 30 and direct the aiming beam and measurement beamtoward the sample material S, with the aiming beam and measurement beamoverlapping on the sample. The aiming beam 20 may be arranged to bedirected along an aiming beam axis 25, while the measurement beam 30 maybe arranged to be directed along a measurement beam axis 35. The aimingbeam axis 25 may be co-axial with measurement beam axis 35.

The sensor or detector of the spectrometer module 160 may comprise oneor more filters configured to transmit the measurement beam 30 butinhibit transmission of the aiming beam 20. In many configurations, thespectrometer module comprises one filter configured to inhibittransmission of visible light, thereby inhibiting transmission ofportions of the aiming beam 20 and measurement beam 30 reflected fromthe sample that comprise visible light. In some configurations, thespectrometer module 160 may comprise a plurality of optical filtersconfigured to inhibit transmission of a portion of the aiming beam 20reflected the sample material S, and to transmit a portion of themeasurement beam 30 reflected from the sample. In configurations of thespectrometer module comprising a plurality of optical channels, thespectrometer module may comprise a plurality of filters wherein eachoptical filter corresponds to an optical channel. Each filter may beconfigured to inhibit transmission of light within a specific rangeand/or within a specific angle of incidence, wherein the filteredspecific range or specific angle of incidence may be specific to thecorresponding channel. In some configurations, each optical channel ofthe spectrometer module may comprise a field of view. The field of view40 of the spectrometer module may comprise a plurality of overlappingfields of view of a plurality of optical channels. The aiming beam andthe measurement beam may overlap with the plurality of overlappingfields of view on the sample S. In many configurations, a diffuser maybe disposed between the plurality of optical filters and the incidentlight from the sample, in which each optical filter corresponds to anoptical channel. In such configurations, the plurality of opticalchannels may comprise similar fields of view through the diffuser, witheach field of view at least partially overlapping with the fields ofview of other optical channels. With the diffuser, the spectrometer maycomprise a wide field of view, for example ±90°.

Optionally, the visible aiming beam 20 may be produced by a light sourceseparate from the illumination module 140. In this case, the separatelight source may be configured to produce the aiming beam such that theaiming beam illuminates a portion of the sample material that overlapswith the measurement area 50 of the sample.

The compact size of the spectrometer 102 can provide a hand held devicethat can be directed (e.g., pointed) at a material to rapidly obtaininformation about the material. As shown in FIGS. 1A and 1B, thespectrometer 102 may have a size and weight such that the spectrometercan be held by a user with only one hand H. The spectrometer can have asize and weight such that the spectrometer can be portable. Thespectrometer can have a weight of about 1 gram (g), 5 g, 10 g, 15 g, 20g, 25 g, 30 g, 35 g, 40 g, 45 g, 50 g, 55 g, 60 g, 65 g, 70 g, 80 g. 85g, 90 g, 95 g, 100 g, 110 g, 120 g, 130 g, 140 g, 150 g, 160 g, 170 g,180 g, 190 g, or 200 g. The spectrometer can have a weight less than 1g. The spectrometer can have a weight greater than 200 g. Thespectrometer can have a weight that is between any of the two valuesgiven above. For example, the spectrometer can have a weight within arange from about 1 g to about 200 g, about 1 g to about 100 g, about 5 gto about 50 g, about 5 g to about 40 g, about 10 g to about 40 g, about10 g to about 30 g, or about 20 g to about 30 g.

The spectrometer can have a total volume of at most about 200 cm³, 150cm³, 100 cm³, 95 cm³, 90 cm³, 85 cm³, 80 cm³, 75 cm³, 70 cm³, 65 cm³, 60cm³, 55 cm³, 50 cm³, 45 cm³, 40 cm³, 35 cm³, 30 cm³, 25 cm³, 20 cm³, 15cm³, 10 cm³, 5 cm³, or 1 cm³. The spectrometer can have a volume lessthan 1 cm³. The spectrometer can have a volume greater than 100 cm³. Thespectrometer can have a volume that is between any of the two valuesgiven above. For example, the spectrometer may have a volume within arange from about 1 cm³ to about 200 cm³, about 40 cm³ to about 200 cm³,about 60 cm³ to about 150 cm³, about 80 cm³ to about 120 cm³, about 80cm³ to about 100 cm³, or about 90 cm³.

The spectrometer shape can comprise a rectangular prism, cylinder, orother three-dimensional shape. The spectrometer can have a length of atmost about 500 mm, 400 mm, 300 mm, 200 mm, 250 mm, 100 mm, 95 mm, 90 mm,85 mm, 80 mm, 75 mm, 70 mm, 65 mm, 60 mm, 55 mm, 50 mm, 45 mm, 40 mm, 35mm, 30 mm, 25 mm, 20 mm, 15 mm, 10 mm, or 5 mm. The spectrometer canhave a length less than 5 mm. The spectrometer can have a length greaterthan 500 mm. The spectrometer can have a length that is between any ofthe two values given above. For example, the spectrometer have a lengthwithin a range from about 10 mm to about 100 mm, about 25 mm to about 75mm, or about 50 mm to about 70 mm. The spectrometer can have a width ofat most about 500 mm, 400 mm, 300 mm, 200 mm, 250 mm, 100 mm, 95 mm, 90mm, 85 mm, 80 mm, 75 mm, 70 mm, 65 mm, 60 mm, 55 mm, 50 mm, 45 mm, 40mm, 35 mm, 30 mm, 25 mm, 20 mm, 15 mm, 10 mm, or 5 mm. The spectrometercan have a width less than 5 mm. The spectrometer can have a widthgreater than 500 mm. The spectrometer can have a width that is betweenany of the two values given above. For example, the spectrometer mayhave a width within a range from about 10 mm to about 75 mm, about 20 mmto about 60 mm, or about 30 mm to about 50 mm. The spectrometer can havea height of at most about 500 mm, 400 mm, 300 mm, 200 mm, 250 mm, 100mm, 95 mm, 90 mm, 85 mm, 80 mm, 75 mm, 70 mm, 65 mm, 60 mm, 55 mm, 50mm, 45 mm, 40 mm, 35 mm, 30 mm, 25 mm, 20 mm, 15 mm, 10 mm, or 5 mm. Thespectrometer can have a height less than 5 mm. The spectrometer can havea height greater than 500 mm. The spectrometer can have a height that isbetween any of the two values given above. For example, the spectrometermay have a height within a range from about 1 mm to about 50 mm, about 5mm to about 40 mm, or about 10 mm to about 20 mm. The spectrometer may,for example, have dimensions within a range from about 0.1 cm×0.1 cm×2cm to about 5 cm×5 cm×10 cm. In the case of a cylindrical spectrometerthe spectrometer can have a radius of at most about 500 mm, 400 mm, 300mm, 200 mm, 250 mm, 100 mm, 95 mm, 90 mm, 85 mm, 80 mm, 75 mm, 70 mm, 65mm, 60 mm, 55 mm, 50 mm, 45 mm, 40 mm, 35 mm, 30 mm, 25 mm, 20 mm, 15mm, 10 mm, or 5 mm. The spectrometer can have a radius less than 5 mm.The spectrometer can have a radius greater than 500 mm. The spectrometercan have a radius that is between any of the two values given above.

One or more of the components of the spectrometer can be powered by abattery. The battery can be on-board the spectrometer. The battery canhave a weight of at most about 50 g, 45 g, 40 g, 35 g, 30 g, 25 g, 20 g,15 g, 10 g, 5 g, 1 g, or 0.1 g. The battery can have a weight less than0.1 g. The battery can have a weight greater than 50 g. The battery canhave a weight that is between any of the two values given above. Forexample, the batter may have a weight that is within a range from about2 g to about 6 g, about 3 g to about 5 g, or about 4 g.

The compact spectrometer 102 may have an optical resolution of less than10 nm, less than 5 nm, less than 4 nm, less than 3 nm, less than 2 nm,less than 1 nm, less than 0.5 nm, or less than 0.1 nm. The spectrometercan have an optical resolution that is between any of the two valuesgiven above. For example, the spectrometer may have an opticalresolution that is within a range from about 0.1 nm to about 100 nm,about 1 nm to about 50 nm, about 1 nm to about 10 nm, or about 2 nm toabout 5 nm. The spectrometer may have an optical resolution ofapproximately 5 nm, which is equivalent to approximately 100 cm⁻¹ at awavelength of about 700 nm and equivalent to approximately 40 cm⁻¹ at awavelength of about 1100 nm. The spectrometer may have an opticalresolution that is between 100 cm⁻¹ and 40 cm⁻¹. The spectrometer canhave a temporal signal-to-noise ratio (SNR) of about 1000 for a singlesensor reading (without averaging, at maximum spectral resolution) for awavelength of about 1000 nm, or an SNR of about 2500 for a wavelength ofabout 850 nm. The compact spectrometer, when configured to performalgorithmic processing or correction of measured spectral data, may beable to detect changes in normalized signals in the order of about1×10⁻³ to about 1×10⁻⁴, or about 5×10⁻⁴. The light source of theillumination module may be configured to have a stabilization time ofless than 1 min, less than 1 s, less than 1 ms, or about 0 s.

Spectrometer Using Secondary Emission Illumination with Filter-BasedOptics

Reference is now made to FIG. 4 , which illustrates non-limitingconfigurations of the compact spectrometer system 100 herein disclosed.The system comprises a spectrometer 102, which comprises various modulessuch as a spectrometer module 160. As illustrated, the spectrometermodule 160 may comprise a diffuser 164, a filter matrix 170, a lensarray 174 and a detector 190.

The spectrometer system may comprise a plurality of optical filters offilter matrix 170. The optical filter can be of any type known in theart. Non-limiting examples of suitable optical filters includeFabry-Perot (FP) resonators, cascaded FP resonators, and interferencefilters. For example, a narrow bandpass filter (≤10 nm) with a wideblocking range outside of the transmission band (at least 200 nm) can beused. The center wavelength (CWL) of the filter can vary with theincident angle of the light impinging upon it.

The central wavelength of the central band can vary by 10 nm or more,such that the effective range of wavelengths passed with the filter isgreater than the bandwidth of the filter. In many instances, the centralwavelength varies by an amount greater than the bandwidth of the filter.For example, the bandpass filter can have a bandwidth of no more than 10nm and the wavelength of the central band can vary by more than 10 nmacross the field of view of the sensor.

The spectrometer system may comprise a filter matrix. The filter matrixcan comprise one or more filters, for example a plurality of filters.The use of a single filter can limit the spectral range available to thespectrometer. A filter can be an element that only permits transmissionof a light signal with a predetermined incident angle, polarization,wavelength, and/or other property. For example, if the angle ofincidence of light is larger than 30°, the system may not produce asignal of sufficient intensity due to lens aberrations and the decreasein the efficiency of the detector at large angles. For an angular rangeof 30° and an optical filter center wavelength (CWL) of ˜850 nm, thespectral range available to the spectrometer can be about 35 nm, forexample. As this range can be insufficient for some spectroscopy basedapplications, configurations with larger spectral ranges may comprise anoptical filter matrix composed of a plurality of sub-filters. Eachsub-filter can have a different CWL and thus covers a different part ofthe optical spectrum. The sub-filters can be configured in one or moreof many ways and be tiled in two dimensions, for example.

Depending on the number of sub-filters, the wavelength range accessibleto the spectrometer can reach hundreds of nanometers. In configurationscomprising a plurality of sub-filters, the approximate Fouriertransforms formed at the image plane (i.e. one per sub-filter) overlap,and the signal obtained at any particular pixel of the detector canresult from a mixture of the different Fourier transforms.

The filter matrixes may be arranged in a specific order to inhibit crosstalk on the detector of light emerging from different filters and tominimize the effect of stray light. For example, if the matrix iscomposed of 3×4 filters then there are 2 filters located at the interiorof the matrix and 10 filters at the periphery of the matrix. The 2filters at the interior can be selected to be those at the edges of thewavelength range. Without being bound by a particular theory, theselected inner filters may experience the most spatial cross-talk but bethe least sensitive to cross-talk spectrally.

The spectrometer module may comprise a lens array 174. The lens arraycan comprise a plurality of lenses. The number of lenses in theplurality of lenses can be determined such that each filter of thefilter array corresponds to a lens of the lens array. Alternatively orin combination, the number of lenses can be determined such that eachchannel through the support array corresponds to a lens of the lensarray. Alternatively or in combination, the number of lenses can beselected such that each region of the plurality of regions of the imagesensor corresponds to an optical channel and corresponding lens of thelens array and filter of the filter array.

The spectrometer system may comprise a detector 190, which may comprisean array of sensors. In many cases, the detector is capable of detectinglight in the wavelength range of interest. The compact spectrometersystem disclosed herein can be used from the UV to the IR, depending onthe nature of the spectrum being obtained and the particular spectralproperties of the sample being tested. The detector can be sensitive toone or more of ultraviolet wavelengths of light, visible wavelengths oflight, or infrared wavelengths of light. In some cases, a detector thatis capable of measuring intensity as a function of position (e.g. anarray detector or a two-dimensional image sensor) is used.

In some instances the spectrometer does not comprise a cylindrical beamvolume hologram (CVBH).

The detector can be located in a predetermined plane. The predeterminedplane can be the focal plane of the lens array. Light of differentwavelengths (X1, X2, X3, X4, etc.) can arrive at the detector as aseries of substantially concentric circles of different radiiproportional to the wavelength. The relationship between the wavelengthand the radius of the corresponding circle may not be linear.

The detector may receive non-continuous spectra, for example spectrathat can be unlike a dispersive element would create. The non-continuousspectra can be missing parts of the spectrum. The non-continuousspectrum can have the wavelengths of the spectra at least in partspatially out of order, for example. In some cases, first shortwavelengths contact the detector near longer wavelengths, and secondshort wavelengths contact the detector at distances further away fromthe first short wavelengths than the longer wavelengths.

The detector may comprise a plurality of detector elements, such aspixels for example. Each detector element may be configured so as toreceive signals of a broad spectral range. The spectral range receivedon a first and second pluralities of detector elements may extend atleast from about 10 nm to about 400 nm. In many instances, spectralrange received on the first and second pluralities of detector elementsmay extend at least from about 10 nm to about 700 nm. In many instances,spectral range received on the first and second pluralities of detectorelements may extend at least from about 10 nm to about 1600 nm. In manyinstances, spectral range received on the first and second pluralitiesof detector elements may extend at least from about 400 nm to about 1600nm. In many instances, spectral range received on the first and secondpluralities of detector elements may extend at least from about 700 nmto about 1600 nm.

The spectrometer system may comprise a diffuser. In configurations inwhich the light emanating from the sample is not sufficiently diffuse, adiffuser can be placed in front of other elements of the spectrometer.The diffuser can be placed in a light path between a light emission anda detector and/or filter. Collimated (or partially collimated light) canimpinge on the diffuser, which then produces diffuse light which thenimpinges on other aspects of the spectrometer, e.g. an optical filter.

In many cases, the lens array, the filter matrix, and the detector arenot centered on a common optical axis. In many cases, the lens array,the filter matrix, and the detector are aligned on a common opticalaxis.

The principle of operation of compact spectrometer may comprise one ormore of the following attributes. Light impinges upon the diffuser andat least a fraction of the light is transmitted through the diffuser.The light next impinges upon the filter matrix at a wide range ofpropagation angles and the spectrum of light passing through thesub-filters is angularly encoded. The angularly encoded light thenpasses through the lens array (e.g. Fourier transform focusing elements)which performs (approximately) a spatial Fourier transform of theangle-encoded light, transforming it into a spatially-encoded spectrum.Finally the light reaches the detector. The location of the detectorelement relative to the optical axis of a lens of the array correspondsto the wavelength of light, and the wavelength of light at a pixellocation can be determined based on the location of the pixel relativeto the optical axis of the lens of the array. The intensity of lightrecorded by the detector element such as a pixel as a function ofposition (e.g. pixel number or coordinate reference location) on thesensor corresponds to the resolved wavelengths of the light for thatposition.

In some cases, an additional filter is placed in front of the compactspectrometer system in order to block light outside of the spectralrange of interest (i.e. to prevent unwanted light from reaching thedetector).

In configurations in which the spectral range covered by the opticalfilters is insufficient, additional sub-filters with differing CWLs canbe used.

In some instances, shutters allow for the inclusion or exclusion oflight from part of the spectrometer 102. For example, shutters can beused to exclude particular sub-filters. Shutters may also be used toexclude individual lens.

FIG. 5 shows a schematic diagram of spectrometer head in accordance withconfigurations. In many cases, the spectrometer 102 comprises aspectrometer head 120. The spectrometer head comprises one or more of aspectrometer module 160, a temperature sensor module 130, and anillumination module 140. Each module, when present, can be covered witha module window. For example, the spectrometer module 160 can comprise aspectrometer window 162, the temperature sensor module 130 can comprisea sensor window 132, and the illumination module 140 can comprise anillumination window 142.

The illumination module and the spectrometer module may be configured tohave overlapping fields of view at the sample. The overlapping fields ofview can be provided in one or more of many ways. For example, theoptical axes of the illumination source, the temperature sensor and thematrix array can extend in a substantially parallel configuration.Alternatively, one or more of the optical axes can be oriented towardanother optical axis of another module.

FIG. 6 shows a schematic drawing of cross-section A of the spectrometerhead of FIG. 3 , in accordance with configurations. In order to lessenthe noise and/or spectral shift produced from fluctuations intemperature, a spectrometer head 120 comprising a temperature sensormodule 130 can be used to measure and record the temperature during themeasurement. The temperature sensor element can measure the temperatureof the sample in response to infrared radiation emitted from the sample,and transmit the temperature measurement to a processor. Accurate and/orprecise temperature measurement can be used to standardize or modify thespectrum produced. For example, different spectra of a given sample canbe measured based on the temperature at which the spectrum was taken. Aspectrum can be stored with metadata relating to the temperature atwhich the spectrum was measure. The temperature sensor module 130 maycomprise a temperature sensor window 132. The temperature sensor windowcan seal the sensor module. The temperature sensor window 132 can bemade of material that is substantially non-transmissive to visible lightand transmits light in the infrared spectrum. The temperature sensorwindow 132 may comprise germanium, for example. The temperature sensorwindow can be about 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0 mmthick.

The temperature sensor can comprise a field of view (herein after “FoV”)limiter. In many instances, the temperature sensor has a field of vieworiented to overlap with a field of view of the detector and a field ofview of an illuminator. For example, the field of view can be limited byan aperture formed in a material supporting the window 132 oftemperature sensor module and the dimensions of the temperature sensor134. In some instances, the temperature sensor module has a limitedfield of view and comprises a heat conductive metal cage disposed on aflex printed circuit board (PCB) 136. The PCB 136 can be mounted on astiffener 138 in order to inhibit movement relative to the other moduleson the sensor head. The flexible circuit board may be backed bystiffener 138 comprising a metal. The temperature sensor 134 can be aremote temperature sensor. The temperature sensor can give a temperaturethat is accurate to within about 5, 4, 3, 2, 1, 0.7, 0.4, 0.3, 0.2 or0.1 degree Celsius of the ambient temperature of the sample. Thetemperature sensor may measure the ambient temperature with precision to3, 2, 1, 0.5, or 0.1 degree Celsius.

The spectrometer head may comprise an illumination module 140. Theillumination module can illuminate a sample with light. In someinstances, the illumination module comprises an illumination window 142.The illumination window can seal the illumination module. Theillumination window can be substantially transmissive to the lightproduced in the illumination module. For example, the illuminationwindow can comprise glass. The illumination module can comprise a lightsource 148. The light source can comprise one or more light emittingdiodes (LED). For example, the light source may comprise a blue LED, redLED, green LED, infrared LED, or a combination thereof.

The light source 148 can be mounted on a mounting fixture 150. Themounting fixture may comprise a ceramic package. For example, the lightfixture can be a flip-chip LED die mounted on a ceramic package. Themounting fixture 150 can be attached to a flexible printed circuit board(PCB) 152 which can optionally be mounted on a stiffener 154 to reducemovement of the illumination module. The flex PCB of the illuminationmodule and the PCT of temperature sensor modules may comprise differentportions of the same flex PCB, which may also comprise portions ofspectrometer PCB.

The wavelength of the light produced by the light source 148 can beshifted by a plate 146. Plate 146 can be a wavelength shifting plate.Plate 146 may comprise phosphor embedded in glass. Alternatively or incombination, plate 146 can comprise a nano-crystal, a quantum dot, orcombinations thereof. The plate can absorb light from the light sourceand release light having a frequency lower than the frequency of theabsorbed light. In some cases, a light source produces visible light,and plate 146 absorbs the light and emits near infrared light. The lightsource may be in close proximity to or directly touching the plate 146.The light source and associated packaging may be separated from theplate by a gap to limit heat transfer. For example, the gap between thelight source and the plate can be at least 0.1, 0.2, 0.3, 0.4, 0.5, 0.6,0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0, 7.0, 8.0,9.0, or 10.0 mm. Alternatively, the light source packaging may touch theplate 146 in order to conduct heat from the plate such that the lightsource packaging comprises a heat sink.

The illumination module can further comprise a light concentrator suchas a parabolic concentrator 144 or a condenser lens in order toconcentrate the light. The parabolic concentrator 144 may be areflector. The parabolic concentrator 144 may comprise stainless steelor gold-plated stainless steel. The concentrator can concentrate lightto a cone. For example, the light can be concentrated to a cone with afield of view of about 30-45, 25-50, or 20-55 degrees.

The illumination module may be configured to transmit light and thespectrometer module may be configured to receive light along opticalpaths extending substantially perpendicular to an entrance face of thespectrometer head. The modules can be configured such that light can betransmitted from one module to an object (such as a sample S) andreflected or scattered to another module which receives the light.

The optical axes of the illumination module and the spectrometer modulemay be configured to be non-parallel such that the optical axisrepresenting the spectrometer module is at an offset angle to theoptical axis of the illumination module. This non-parallel configurationcan be provided in one or more of many ways. For example, one or morecomponents can be supported on a common support and offset in relationto an optic such as a lens in order to orient one or more optical axestoward each other. Alternatively or in combination, a module can beangularly inclined with respect to another module. The optical axis ofeach module may be aligned at an offset angle of greater than 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25, 30, 35, 40, 45, or 50degrees. The illumination module and the spectrometer module may beconfigured to be aligned at an offset angle of less than 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25, 30, 35, 40, 45, or 50 degrees.The illumination module and the spectrometer module can be configured tobe aligned at an offset angle between than 1-10, 11-20, 21-30, 31-40 or41-50 degrees. The offset angle of the modules may be set firmly and notadjustable, or the offset angle may adjustable. The offset angle of themodules may be automatically selected based on the distance of thespectrometer head from the sample. Two modules may have parallel opticalaxes. Two or more modules may have offset optical axes. In someinstances, the modules can have optical axes offset such that theyconverge on a sample. The modules can have optical axes offset such thatthey converge at a set distance. For example, the modules can haveoptical axes offset such that they converge at a distance of about 10,20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, or500 mm away.

FIG. 7 shows a schematic drawing of cross-section B of the spectrometerhead of FIGS. 3 and 4 , in accordance with configurations. Thespectrometer head 120 may comprise spectrometer module 160. Thespectrometer module can be sealed by a spectrometer window 162. Thespectrometer window 162 may be selectively transmissive to light withrespect to the wavelength in order to analyze the spectral sample. Forexample, spectrometer window 162 can be an IR-pass filter. In someinstances, the window 162 can be glass. The spectrometer module cancomprise one or more diffusers. For example, the spectrometer module cancomprise a first diffuser 164 disposed below the spectrometer window162. The first diffuser 164 can distribute the incoming light. Forexample, the first diffuser can be a cosine diffuser. Optionally, thespectrometer module may comprise a light filter 188. Light filter 188can be a thick IR-pass filter. For example, filter 188 can absorb lightbelow a threshold wavelength. Filter 188 can absorb light with awavelength below about 1000, 950, 900, 850, 800, 750, 700, 650, or 600nm. The spectrometer module may further comprise a second diffuser 166.The second diffuser can generate Lambertian light distribution at theinput of the filter matrix 170. The filter assembly can be sealed by aglass plate 168. Alternatively or in combination, the filter assemblycan be further supported by a filter frame 182, which can attach thefilter assembly to the spectrometer housing 180. The spectrometerhousing 180 can hold the spectrometer window 162 in place and furtherprovide mechanical stability to the module.

The first filter and the second filter can be arranged in one or more ofmany ways to provide a substantially uniform light distribution to thefilters. The substantially uniform light distribution can be uniformwith respect to an average energy to within about 25%, for example towithin about 10%, for example. The first diffuser may distribute theincident light energy spatially on the second diffuser with asubstantially uniform energy distribution profile. The first diffusermay make the light substantially homogenous with respect to angulardistribution. The second diffuser can further diffuse the light energyof the substantially uniform energy distribution profile to asubstantially uniform angular distribution profile, such that the lighttransmitted to each filter can be substantially homogenous both withrespect to the spatial distribution profile and the angular distributionprofile of the light energy incident on each filter. For example, theangular distribution profile of light energy onto each filter can beuniform to within about +/−25%, for example substantially uniform towithin about +/−10%.

The spectrometer module comprises a filter matrix 170. The filter matrixcan comprise one or more filters. In many instances, the filter matrixcomprises a plurality of filters.

In some instances, each filter of the filter matrix 170 is configured totransmit a range of wavelengths distributed about a central wavelength.The range of wavelengths can be defined as a full width half maximum(hereinafter “FWHM”) of the distribution of transmitted wavelengths fora light beam transmitted substantially normal to the surface of thefilter as will be understood by a person of ordinary skill in the art. Awavelength range can be defined by a central wavelength and by aspectral width. The central wavelength can be the mean wavelength oflight transmitted through the filter, and the band spectral width of afilter can be the difference between the maximum and the minimumwavelength of light transmitted through the filter. Each filter of theplurality of filters may be configured to transmit a range ofwavelengths different from other filters of the plurality. The range ofwavelengths overlaps with ranges of said other filters of the pluralityand wherein said each filter comprises a central wavelength differentfrom said other filters of the plurality.

The filter array comprises a substrate having a thickness and a firstside and a second side, the first side oriented toward the diffuser, thesecond side oriented toward the lens array. In some instances, eachfilter of the filter array comprises a substrate having a thickness anda first side and a second side, the first side oriented toward thediffuser, the second side oriented toward the lens array. The filterarray can comprise one or more coatings on the first side, on the secondside, or a combination thereof. Each filter of the filter array cancomprise one or more coatings on the first side, on the second side, ora combination thereof. In some instances, each filter of the filterarray comprises one or more coatings on the second side, oriented towardthe lens array. In some instances, each filter of the filter arraycomprises one or more coatings on the second side, oriented toward thelens array and on the first side, oriented toward the diffuser. The oneor more coatings on the second side can be an optical filter. Forexample, the one or more coatings can permit a wavelength range toselectively pass through the filter. Alternatively or in combination,the one or more coatings can be used to inhibit cross-talk among lensesof the array. In some instances, the plurality of coatings on the secondside comprises a plurality of interference filters, said each of theplurality of interference filters on the second side configured totransmit a central wavelength of light to one lens of the plurality oflenses. In some instances, the filter array comprises one or morecoatings on the first side of the filter array. The one or more coatingson the first side of the array can comprise a coating to balancemechanical stress. In some instances, the one or more coatings on thefirst side of the filter array comprises an optical filter. For example,the optical filter on the first side of the filter array can comprise anIR pass filter to selectively pass infrared light. In many instances,the first side does not comprise a bandpass interference filter coating.In some instances, the first does not comprise a coating.

In many instances, the array of filters comprises a plurality ofbandpass interference filters on the second side of the array. Theplacement of the fine frequency resolving filters on the second sideoriented toward the lens array and apertures can inhibit cross-talkamong the filters and related noise among the filters. In manyinstances, the array of filters comprises a plurality of bandpassinterference filters on the second side of the array, and does notcomprise a bandpass interference filter on the first side of the array.

In many instances, each filter defines an optical channel of thespectrometer. The optical channel can extend from the filter through anaperture and a lens of the array to a region of the sensor array. Theplurality of parallel optical channels can provide increased resolutionwith decreased optical path length.

The spectrometer module can comprise an aperture array 172. The aperturearray can prevent cross talk between the filters. The aperture arraycomprises a plurality of apertures formed in a non-opticallytransmissive material. In some instances, the plurality of apertures isdimensioned to define a clear lens aperture of each lens of the array,wherein the clear lens aperture of each lens is limited to one filter ofthe array. In some instances, the clear lens aperture of each lens islimited to one filter of the array.

In many instances the spectrometer module comprises a lens array 174.The lens array can comprise a plurality of lenses. The number of lensescan be determined such that each filter of the filter array correspondsto a lens of the lens array. Alternatively or in combination, the numberof lenses can be determined such that each channel through the supportarray corresponds to a lens of the lens array. Alternatively or incombination, the number of lenses can be selected such that each regionof the plurality of regions of the image sensor corresponds to anoptical channel and corresponding lens of the lens array and filter ofthe filter array.

In many instances, each lens of the lens array comprises one or moreaspheric surfaces, such that each lens of the lens array comprises anaspherical lens. In many instances, each lens of the lens arraycomprises two aspheric surfaces. Alternatively or in combination, one ormore individual lens of the lens array can have two curved opticalsurfaces wherein both optical surfaces are substantially convex.Alternatively or in combination, the lenses of the lens array maycomprise one or more diffractive optical surfaces.

In many instances, the spectrometer module comprises a support array176. The support array 176 comprises a plurality of channels 177 definedwith a plurality of support structures 179 such as interconnectingannuli. The plurality of channels 177 may define optical channels of thespectrometer. The support structures 179 can comprises stiffness to addrigidity to the support array 176. The support array may comprise astopper to limit movement and fix the position the lens array inrelation to the sensor array. The support array 176 can be configured tosupport the lens array 174 and fix the distance from the lens array tothe sensor array in order to fix the distance between the lens array andthe sensor array at the focal length of the lenses of the lens array. Inmany instances, the lenses of the array comprise substantially the samefocal length such that the lens array and the sensor array are arrangedin a substantially parallel configuration.

The support array 176 can extend between the lens array 174 and thestopper mounting 178. The support array 176 can serve one or morepurposes, such as 1) providing the correct separation distance betweeneach lens of lens array 170 and each region of the plurality of regionsof the image sensor 190, and/or 2) preventing stray light from enteringor exiting each channel, for example. In some instances, the height ofeach support in support array 176 is calibrated to the focal length ofthe lens within lens array 174 that it supports. In some instances, thesupport array 176 is constructed from a material that does not permitlight to pass such as substantially opaque plastic. In some instances,support array 176 is black, or comprises a black coating to furtherreduce cross talk between channels. The spectrometer module can furthercomprise a stopper mounting 178 to support the support array. In manyinstances, the support array comprises an absorbing and/or diffusivematerial to reduce stray light, for example.

In many instances, the support array 176 comprises a plurality ofchannels having the optical channels of the filters and lenses extendingtherethrough. In some instances, the support array comprise a singlepiece of material extending from the lens array to the detector (i.e.CCD or CMOS array).

The lens array can be directly attached to the aperture array 172, orcan be separated by an air gap of at least 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 12, 14, 16, 18, 20, 30, 40, or 50 micrometers. The lens array can bedirectly on top of the support array 178. Alternatively or incombination, the lens array can be positioned such that each lens issubstantially aligned with a single support stopper or a single opticalisolator in order to isolate the optical channels and inhibitcross-talk. In some instances, the lens array is positioned to be at adistance approximately equal to the focal length of the lens away fromthe image sensor, such that light coming from each lens is substantiallyfocused on the image sensor.

In some instances, the spectrometer module comprises an image sensor190. The image sensor can be a light detector. For example, the imagesensor can be a CCD or 2D CMOS or other sensor, for example. Thedetector can comprise a plurality of regions, each region of saidplurality of regions comprising multiple sensors. For example, adetector can be made up of multiple regions, wherein each region is aset of pixels of a 2D CMOS. The detector, or image sensor 190, can bepositioned such that each region of the plurality of regions is directlybeneath a different channel of support array 176. In many instances, anisolated light path is established from a single of filter of filterarray 170 to a single aperture of aperture array 172 to a single lens oflens array 174 to a single stopper channel of support array 176 to asingle region of the plurality of regions of image sensor 190.Similarly, a parallel light path can be established for each filter ofthe filter array 170, such that there are an equal number of parallel(non-intersecting) light paths as there are filters in filter array 170.

The image sensor 190 can be mounted on a flexible printed circuit board(PCB) 184. The PCB 184 can be attached to a stiffener 186. In someinstances, the stiffener comprises a metal stiffener to prevent motionof the spectrometer module relative to the spectrometer head 120.

FIG. 8 shows an isometric view of a spectrometer module 160 inaccordance with configurations. The spectrometer module 160 comprisesmany components as described herein. In many instances, the supportarray 176 can be positioned on a package on top of the sensor. In manyinstances, the support array can be positioned over the top of the baredie of the sensor array such that an air gap is present. The air gap canbe less than 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1 micrometer(s).

FIG. 9 shows the lens array 174 within the spectrometer module 160, inaccordance with configurations. This isometric view shows the apertures194 formed in a non-transmissive material of the aperture array 172 inaccordance with configurations. In many instances, each channel of thesupport array 176 is aligned with a filter of the filter array 170, alens of the lens array 174, and an aperture 194 of the aperture array inorder to form a plurality of light paths with inhibited cross talk.

The glass-embedded phosphor of plate 146 may be a near-infrared (NIR)phosphor, capable of emitting infrared or NIR radiation in the rangefrom about 700 nm to about 1100 nm.

The light filter 188 may be configured to block at least a portion ofvisible radiation included in the incident light.

In some cases, the first wavelength range of the first filter and thesecond wavelength range of the second filter fall within a wavelengthrange of about 400 nm to about 1100 nm. In some instances, the secondwavelength range overlaps the first wavelength range by at least 2% ofthe second wavelength range. In some instances, the second wavelengthrange overlaps the first wavelength range by an amount of about 1% toabout 5% of the second wavelength range. The overlap in the range ofwavelengths of the filters may be configured to provide algorithmiccorrection of the gains across different channels, for example acrossthe outputs of a first filter element and a second filter element.

The coating of the filter array and/or the support array may comprise ablack coating configured to absorb most of the light that hits thecoated surface. For example, the coating may comprise a coatingcommercially available from Anoplate (as described onhttp://www.anoplate.com/capabilities/anoblack_ni.html), Acktar (asdescribed on the world wide web at the Acktar website, www.acktar.com),or Avian Technologies (as described onhttp://www.aviantechnologies.com/products/coatings/diffuse_black.php),or other comparable coatings.

The stopper and the image sensor may be configured to have matchingcoefficients of thermal expansion (CTE). For example, the stopper andthe image sensor may be configured to have a matching CTE of about 710⁻⁶ K⁻¹. In order to match the CTE between the stopper and the imagesensor where the stopper and image sensor have different CTEs, a liquidcrystal polymer, such as Vectra E130, may be applied between the stopperand the image sensor.

The lens may be configured to introduce some distortion in the output ofthe lens, in order to improve performance in analyzing the obtainedspectral data. The filters described herein may typically allowtransmission of a specific wavelength for a specific angle ofpropagation of the incident light beam. As the light transmitted throughthe filters pass through the lens, the output of the lens may generateconcentric rings on the sensor for different wavelengths of incidentlight. With typical spherical lens performance, as the angle ofincidence grows larger, the concentric ring for that wavelength becomesmuch thinner (for a typical light bandwidth of ˜5 nm). Such variance inthe thickness of the rings may cause reduced linearity and relatedperformance in analyzing the spectral data. To overcome thisnon-linearity, some distortion may be introduced into the lens, so as toreduce the thickness of the rings that correspond to incident lighthaving smaller angles of propagation, and increase the thickness of therings that correspond to incident light having larger angles ofpropagation, wherein non-linearity of ring size related to incidentangle is decreased. Lenses configured to produce such distortion in theoutput can produce a more even distribution of ring thicknesses alongthe supported range of angles of incidence, consequently improvingperformance in the analysis of the generated spectral data. Thedistortion can be provided with one or more aspheric lens profiles toincrease the depth of field (DoF) and increase the size of the pointspread function (PSF) as described herein.

FIG. 10 shows a schematic drawing of a cross-section B of an alternativeembodiment of the spectrometer head of FIG. 5 . In some instances, thespectrometer module may be configured to purposefully induce cross-talkamong sensor elements. For example, the spectrometer module may comprisethe filter matrix and lens array as shown in FIG. 7 , but omit one ormore structural features that isolate the optical channels, such as theaperture array 172 or the isolated channels 177 of the support array176. Without the isolated optical channels, light having a particularwavelength received by the first filter may result in a pattern ofnon-concentric rings on the detector. In addition, a first range ofwavelengths associated with a first filter may partially overlap asecond range of wavelengths associated with a second filter. Without theisolated optical channels, at least one feature in the pattern of lightoutput by a first filter may be associated with at least one feature inthe pattern of light output by a second filter. For example, when lightcomprising two different wavelengths, separated by at least five timesthe spectral resolution of the device, passes through the filter matrix,the light from at least two filters of the filter matrix may impinge onat least one common pixel of the detector. The spectrometer module mayfurther comprise at least one processing device configured to stitchtogether light output by multiple filters to generate or reconstruct aspectrum associated with the incident light. Inducing cross-talk amongsensor elements can have the advantage of increasing signal strength,and of reducing the structural complexity and thereby the cost of theoptics.

Referring again to FIG. 6 , the illumination module 140 can beconfigured to produce an optical beam 10, which may comprise a visibleaiming beam 20 and a measurement beam 30. The aiming beam 20 andmeasurement beam 30 may be produced by the same light source 148, whichmay generate light including visible light. As described herein, theillumination module 140 may comprise a plate 146, such as a phosphorembedded glass plate. The plate may be configured to absorb a portion ofthe optical beam 10 produced by the light source 148, such that theabsorbed light generates an electronic effect resulting in an emissionof light with a wavelength different from the wavelength of the absorbedlight. Alternatively or in combination, a portion of the optical beam 10produced by light source 148 may be configured to be transmitted throughplate 146 without being absorbed or wavelength-shifted. The unabsorbed,transmitted light can form the visible aiming beam 20, which can helpthe user visualize of the measurement area of a sample. A portion of theoptical beam 10 may be wavelength-shifted by the plate 146 and can formthe measurement beam 30, which may comprise light outside the visiblespectrum and/or light in the visible spectrum, as described herein. Forexample, measurement beam 30 may comprise near infrared light. Parabolicconcentrator 144 may be arranged to receive the aiming beam 20 and themeasurement beam 30 and direct the aiming beam and measurement beamtoward a sample material S. As described herein, the aiming beam 20 andmeasurement beam 30 may be partially or completely overlapping, aligned,or coaxial. For example, the aiming beam 20 may be arranged to bedirected along an aiming beam axis 25, while the measurement beam 30 maybe arranged to be directed along a measurement beam axis 35, and theaiming beam axis 25 may be co-axial with measurement beam axis 35. Theaiming beam and measurement beam may overlap on the sample.

The power or visible light output of the aiming beam 20 may varydepending on the amount of optical beam 10 that is configured to passthrough the plate 146 without being absorbed or wavelength-shifted.About 0.1% to about 10%, about 0.5% to about 5%, about 1% to about 4%,or about 2% to about 3% of optical beam 10 may be transmitted throughplate 146 without being wavelength-shifted. The transmission of theoptical beam 10 through plate 146 may be affected by the thickness ofthe plate 146. Further, the transmission of the optical beam 10 throughplate 146 may be affected by the type of light source 148. For example,different types of light sources can be absorbed by the plate 146 atdifferent efficiencies, consequently affecting the amount of light thatis transmitted through the plate 146 without being wavelength-shifted.For a light source 148 comprising a blue LED and a plate 146 comprisingphosphor-embedded glass, about 10 mW to about 15 mW (or about 0.4 toabout 0.6 lumens) of light may transmit through the plate 146 to formthe aiming beam 20. By comparison, light produced by a light sourcecomprising a red LED may not absorb as efficiently by aphosphor-embedded glass plate, and consequently more light, for exampleabout 15 mW to about 30 mW (or about 1 to about 2 lumens) of the light,may transmit through the plate to form the aiming beam 20.

The spectrometer module 160 may comprise one or more filters configuredto transmit the measurement beam 30 but inhibit transmission of theaiming beam 20. In many configurations, the spectrometer modulecomprises one filter, such as light filter 188, configured to inhibittransmission of visible light, thereby inhibiting transmission ofportions of the aiming beam 20 and measurement beam 30 reflected fromthe sample that comprise visible light. In some configurations, thespectrometer module may comprise a plurality of optical filtersconfigured to inhibit transmission of a portion of the aiming beam 20reflected the sample material S, and to transmit a portion of themeasurement beam 30 reflected from the sample. For example, theplurality of optical filters may comprise the optical filters of thefilter matrix 170, wherein each filter in the filter matrix 170corresponds to an optical channel of the plurality of channels 177. Eachfilter may be configured to inhibit transmission of light within aspecific range and/or within a specific angle of incidence, wherein thefiltered specific range or specific angle of incidence may be specificto the corresponding channel. In some configurations, each opticalchannel may comprise a field of view. The field of view of thespectrometer module 160 may hence comprise a plurality of overlappingfields of view of the plurality of optical channels 177. The aiming beam20 and the measurement beam 30 may overlap with the plurality ofoverlapping fields of view on the sample S.

Spectrometer Using Multiple Illumination Sources

FIG. 11 shows a schematic diagram of an alternative embodiment of thespectrometer head 120. The spectrometer head 120 comprises anillumination module 140, a spectrometer module 160, a control board 105,and a processor 106. The spectrometer 102 further comprises atemperature sensor module 130 as described herein, configured to measureand record the temperature of the sample in response to infraredradiation emitted from the sample. In addition to the temperature sensormodule 130, the spectrometer 102 may also comprise a separatetemperature sensor 203 for measuring the temperature of the light sourcein the illumination module 140.

FIG. 12 shows a schematic diagram of a cross-section of the spectrometerhead of FIG. 11 (the sample temperature sensor 130 and the light sourcetemperature sensor 203 are not shown). The spectrometer head comprisesan illumination module 140 and a spectrometer module 160.

The illumination module 140 comprises at least two light sources, suchas light-emitting diodes (LEDs) 210. The illumination module maycomprise at least about 10 LEDs. The illumination module 140 furthercomprises a radiation diffusion unit 213 configured to receive theradiation emitted from the array of LEDs 210, and provide as an outputillumination radiation for use in analyzing a sample material. Theradiation diffusion unit may comprise one or more of a first diffuser215, a second diffuser 220, and one lens 225 disposed between the firstand second diffusers. The radiation diffusion unit may further compriseadditional diffusers and lenses. The radiation diffusion unit maycomprise a housing 214 to support the first diffuser and the seconddiffuser with fixed distances from the light sources. The inner surfaceof the housing 214 may comprise a plurality of light absorbingstructures 216 to inhibit reflection of light from an inner surface ofthe housing. For example, the plurality of light absorbing structuresmay comprise one or more of a plurality of baffles or a plurality ofthreads, as shown in FIG. 12 . A cover glass 230 may be provided tomechanically support and protect each diffuser. Alternatively or incombination with the LEDs, the at least two light sources may compriseone or more lasers.

The array of LEDs 210 may be configured to generate illumination lightcomposed of multiple wavelengths. Each LED may be configured to emitradiation within a specific wavelength range, wherein the wavelengthranges of the plurality of LEDs may be different. The LEDs may havedifferent specific power, peak wavelength and bandwidth, such that thearray of LEDs generates illumination that spans across the spectrum ofinterest. There can be between a few LEDs and a few tens of LEDs in asingle array.

In some instances, the LED array is placed on a printed circuit board(PCB) 152. In order to reduce the size, cost and complexity of the PCBand LED driving electronics and reduce the number of interconnect lines,the LEDs may preferably be arranged in rows and columns, as shown inFIG. 13 . The LED array may comprise a packaged LED array 1300 as shown,comprising a 2-dimensional array of LEDs 210, wherein the array may beabout 14 mm in width 1305 and about 15 mm in length 1310, for example.The LED array may comprise a dice array 1315 as shown, which may beabout 2.8 mm in width 1320 and comprise about 46 LEDs covering aspectral range of about 375 nm to about 1550 nm, for example. All anodeson the same row may be connected together and all cathodes on the samecolumn may be connected together (or vice versa). For example, the LEDin the center of the array may be turned on when a transistor connectsthe driving voltage to the anodes' fourth row and another transistorconnects the cathodes' fourth column to a ground. None of the other LEDsis turned on at this state, as either its anodes are disconnected frompower or its cathodes are disconnected from the ground. Preferably, theLEDs are arranged according to voltage groups, to simplify the currentcontrol and to improve spectral homogeneity (LEDs of similar wavelengthsare placed close together). While bi-polar transistors are providedherein as examples, the circuit may also use other types of switches(e.g., field-effect transistors).

The LED currents can be regulated by various means as known to thoseskilled in the art. In some instances, Current Control Regulator (CCR)components may be used in series to each anode row and/or to eachcathode column of the array. In some instances, a current control loopmay be used instead of the CCR, providing more flexibility and feedbackon the actual electrode currents. Alternatively, the current may bedetermined by the applied anode voltages, though this method should beused with care as LEDs can vary significantly in their current tovoltage characteristics.

An optional voltage adjustment diode can be useful in reducing thedifference between the LED driving voltages of LEDs sharing the sameanode row, so that they can be driven directly from the voltage sourcewithout requiring a current control circuit. The optional voltageadjustment diode can also help to improve the stability and simplicityof the driving circuit. These voltage adjustment diodes may be selectedaccording to the LEDs' expected voltage drops across the row, inopposite tendency, so that the total voltage drop variation along ashared row is smaller.

Referring to FIG. 12 , the radiation diffusion unit 213, positionedabove the LED array, is configured to mix the illumination emitted byeach of the LEDs at different spatial locations and with differentangular characteristics, such that the spectrum of illumination of thesample will be as uniform as possible across the measured area of thesample. What is meant by a uniform spectrum is that the relations ofpowers at different wavelengths do not depend on the location on thesample. However, the absolute power can vary. This uniformity is highlypreferable in order to optimize the accuracy of the reflection spectrummeasurement.

The first diffuser 215, preferably mechanically supported and protectedby a cover glass 230, may be placed above the array of LEDs 210. Thediffuser may be configured to equalize the beam patterns of thedifferent LEDs, as the LEDs will typically differ in their illuminationprofiles. Regardless of the beam shape of any LED, the light that passesthrough the first diffuser 215 can be configured to have a Lambertianbeam profile, such that the emitted spectrum at each of the directionsfrom first diffuser 215 is uniform. Ideally, the ratios between theilluminations at different wavelengths do not depend on the direction tothe plane of the first diffuser 215, as observed from infinity. Suchdirections are indicated schematically by the dashed lines shown in FIG.14 , referring to the directions of rays at the output of the firstdiffuser 215 towards the first surface of lens 225.

The first diffuser 215 is preferably placed at the aperture plane of thelens 225. Thus, parallel rays can be focused by the lens to the samelocation on the focal plane of the lens, where the second diffuser 220is placed (preferably supported and protected by cover glass 230). Sinceall illumination directions at the output of the first diffuser 215 havethe same spectrum, the spectrum at the input plane of the seconddiffuser 220 can be uniform (though the absolute power may vary). Thesecond diffuser 220 can then equalize the beam profiles from each of thelocations in its plane, so that the output spectrum is uniform both inlocation and in direction, leading to uniform spectral illuminationacross the sample irrespective of the sample distance from the device(when the sample is close to the device it is more affected by thespatial variance of spectrum, and when the sample is far from the deviceit is more affected by the angular variation of the spectrum).

In designing the radiation diffusion unit 213 configured to improvespectral uniformity, size and power may be traded off in order toachieve the required spectral uniformity. For example, as shown in FIG.15A, the radiation diffusion unit 213 may be duplicated (additionaldiffusers and lenses added), or as shown in FIG. 15B, the radiationdiffusion unit 213 may be configured with a longer length between thefirst and second diffusers, in order to achieve increased uniformitywhile trading off power. Alternatively, if uniformity is less important,some elements in the optics can be omitted (e.g., first diffuser orlens), or simplified (e.g., weaker diffuser, simpler lens).

Referring back to FIG. 12 , the spectrometer module 160 comprises one ormore photodiodes 263 that are sensitive to the spectral range ofinterest. For example, a dual Si—InGaAs photodiode can be used tomeasure the sample reflection spectrum in the range of about 400 nm toabout 1750 nm. The dual photodiode structure is composed of twodifferent photodiodes positioned one above the other, such that theycollect illumination from essentially the same locations in the sample.

The one or more photodiodes 263 are preferably placed at the focal planeof lens 225, as shown in FIG. 12 . The lens 225 can efficiently collectthe light from a desired area in the sample to the surface of thephotodiode. Alternatively, other light collection methods known in theart can be used, such as a Compound Parabolic Concentrator.

The photodiode current can be detected using a trans-impedanceamplifier. For the dual photodiode architecture embodiment, thephotocurrent can first be converted from current to voltage usingresistors with resistivity that provides high gain on the one hand toreduce noise, while having a wide enough bandwidth and no saturation onthe other hand. An operational amplifier can be connected inphotovoltaic mode amplification to the photodiodes, for minimum noise.Voltage dividers can provide a small bias to the operational amplifier(Op Amp) to compensate for possible bias current and bias voltage at theOp Amp input. Additional amplification may be preferable with voltageamplifiers.

In the embodiment of the spectrometer head shown in FIG. 12 , eachphotodiode 263 is responsive to the illumination from typically manyLEDs (or wavelengths). In order to identify the relative contribution oflight from each of the LEDs, the LED current may be modulated, then thedetected photocurrent of the photodiodes may be demodulated.

In some instances, the modulation/demodulation may be achieved by timedivision multiplexing (TDM). In TDM, each LED is switched “on” in adedicated time slot, and the photocurrent sampled in synchronization tothat time slot represents the contribution of the corresponding LED andits wavelength. Black level and ambient light is measured at the “off”times between “on” times.

In some instances, the modulation/demodulation may be achieved byfrequency division modulation (FDM). In FDM, each LED is modulated at adifferent frequency. This modulation can be with any waveform, andpreferably by square wave modulation for best efficiency and simplicityof the driving circuit. This means that at any given time, one or moreof the LEDs can be “on” at the same time, and one of more of the LEDscan be “off” at the same time. The detected signal is decomposed to thedifferent LED contributions, for example by using matched filter or fastFourier transform (FFT), as known to those skilled in the art.

FDM may be preferable with respect to TDM as FDM can provide lower peakcurrent than TDM for the same average power, thus improving theefficiency of the LEDs. The higher efficiency allows for lower LEDtemperatures, which in turn provide better LED spectrum stability.Another advantage of FDM is that FDM has lower electromagneticinterference than TDM (since slower current slopes can be used), andsmaller amplification channel bandwidth requirement than TDM.

In some instances, the modulation/demodulation may be achieved byamplitude modulation, each at a different frequency.

When the LED array uses a shared-electrodes architecture, a single LEDcan be turned “on” when the corresponding row and column are connected(e.g., anode to power and cathode to GND). However, when more than onerow and one column is switched “on”, all the LEDs sharing the connectedrows and columns will be switched on. This can complicate themodulation/demodulation scheme. In order to resolve such a complication,TDM may be used, wherein a single row and a single column is enabled ateach “on” time slot. Alternatively, combined TDM and FDM may be used,wherein a single row is selected with TDM, and FDM is applied on thecolumns (or vice versa). Alternatively, a 2-level FDM may be used,wherein each row and each column is modulated at different frequencies.The LEDs can be decoupled using matched filter or spectrum analysis,while taking special care to avoid overlapping harmonics of basefrequencies.

Referring again to FIG. 12 , the illumination module 140 can beconfigured to produce an optical beam 10, which may comprise a visibleaiming beam 20 and a measurement beam 30. As described herein, thevisible aiming beam 20 and measurement beam 30 may be partially orcompletely overlapping, aligned, or coaxial (e.g., around co-axialaiming beam axis 25 and measurement beam axis 35). The aiming beam 20and measurement beam 30 may be produced by the same light source, whichmay comprise two or more LEDs 210. One or more of the two or more LEDs210 may produce light in the visible spectrum, and output enough visiblelight to form the aiming beam 20. All or a portion of the light outputfrom the one or more LEDs in the visible range may form the visibleaiming beam 20. Optionally, operation of one or more of the LEDs 210 maybe adjusted such that the visibility of the aiming beam 20 is enhanced.

Additional Disclosure Relating to Spectrometer Using Secondary EmissionIllumination with Filter-Based Optics

FIGS. 16A and 16B are schematic drawings of cross-sectional views of anoptical subassembly 165 of spectrometer module 160, in accordance withconfigurations. FIG. 16A shows an isometric cross-sectional view, whileFIG. 16B shows a cross-sectional view of the optical subassembly. Theoptical subassembly 165 comprises a filter array 170, aperture array172, lens array 174, and support array 176 as described herein. Theoptical subassembly may be adhesively coupled to the image sensor 190,which may further coupled to a PCB 184 and/or a stiffer 186 as describedherein.

The coated side 173 of the filter array 170 and the aperture array 172may be configured to have as small a gap 169 as possible. In preferredembodiments, the gap is substantially zero, such that the coated side ofthe filter array is in contact with the aperture array. The elements ofthe optical subassembly 165 may be designed such that the position ofthe filter array 170 along the optical axis (Z-axis) is determined bythe thickness of the lens array 174 and the aperture array 172, suchthat the filter array physically contacts the lens array, and thesubassembly comprising the filter array, lens array, and aperture arraycan be bonded to the support array 176.

The spaces 171 between the filters of the filter array 170 can be filledwith an index-matched material to enable homogeneous illumination at theplane of the coated side 173 of the filter array. This can accomplished,for example, using an optical adhesive 167 that can also encapsulate andthereby provide structural support to the filter array. The opticaladhesive 167 may be optically clear and comprise an index of refractionsimilar to the substrate material of the filter array 170 (e.g., fusedglass). The optical adhesive 167 may comprise one or more of a varietyof chemicals such as silicone and epoxy, and may be cured using one ormore curing mechanisms known in the art, such as UV-curing.

Preferably, the positions of the filter array 170, aperture array 172,and lens array 174 are tightly controlled, so as to reduce chipping andpeeling of the filter coating at the edges of the filters, and tominimize the necessary filter area in order to reduce cost. For example,the positions of the filter array, aperture array, and lens array may besubstantially fixed relative to one another. The support array 176 maybe configured to align the lens array, the aperture array, and thefilter array, for example.

The filter array 170 can be configured to have top and bottom surfacesthat are parallel to one another, such that the filter array can supportthe assembly of additional elements of the spectrometer module (e.g.,referring again to FIG. 7 , light filter 188 sandwiched between thediffusers 164 and 166, spectrometer window 162). For example, a glassplate 168 may be placed above the filter array 170. The filter frame 182may be configured to support and thereby determine the position of theglass plate 168, such that the position of the glass plate isindependent of any differences in the thickness of the filters withinthe filter array 170.

FIG. 17 is a schematic drawing of a portion of an optical subassembly165, assembled according to one of many exemplary methods. To assemblethe optical subassembly 165, the filter array 170 may be bonded to arigid aperture array 172 via an adhesive. The aperture array can havegrooves 175 on the surface facing the filter array, the groovesconfigured to collect excess adhesive and prevent the adhesive fromreaching into the apertures 194. Grooves 175 may comprise, for example,circular grooves positioned about the circumference of each aperture194. The filter array may be bonded to the aperture array using apick-and-place machine, for example. The filter frame 182 may be coupledto the subassembly comprising the bonded filter array and aperturearray, and frame may be filled with an optical adhesive 167 as describedherein.

Alternatively, in embodiments comprising a filter array 170 havingfilters of uniform thickness, the optical subassembly 165 may beassembled such that the filter array 170 is in direct contact with theglass plate 168. For example, the top surface of the filter array may beplaced flush against the bottom surface of the glass plate. Such anassembly configuration can eliminate the need to bond the filter arrayto the aperture array 172, since the filter array can be retained in asubstantially fixed position by the glass plate 168. Without the need tosupport bonding of the filter array, the aperture array can besimplified in construction and/or have fewer constraints on design. Forexample, the aperture array can be made without the grooves 175, and/orbe made from a more flexible material.

Filter Coatings

Referring again to FIG. 4 , an exemplary optical layout for the compactspectrometer system 100 herein disclosed comprises a diffuser 164,filter array 170, lens array 174, and detector 190. Incident light 200,comprising light reflected from a sample being measured by thespectrometer, is diffusely scattered by diffuser 164, and then filteredby filter array 170. As described herein, each of the filters in thefilter array can be tuned to filter a specific wavelength band, based onthe incidence angle of the light 200. Therefore, the light emerging fromthe filters can be spectrally resolved according to the incidence angle.Lens array 174 can then focus the light onto detector 190, such that theimage formed on the detector from a particular filter in filter array170 is a set of concentric rings, each ring corresponding to theintensity of light at a particular wavelength range.

It is helpful when the intensity of light in each ring, corresponding tolight of a particular wavelength, is affected by the intensity ofillumination at that wavelength on diffuser 164, but does not depend onthe position of the illumination on the diffuser 164. In order to reducethe dependence of measured light intensity on the position of the lighthitting the diffuser, the diffuser 164 may be placed at the apertureplane of the lens array 174. Placing the diffuser farther from the lensaperture plane may result in variations in the spatial distribution oflight on the diffuser, translating into variations in the intensitydistribution in the ring images on the image sensor 190. Such an effectcan decrease the accuracy of the spectrometer.

To reduce the system's sensitivity to the spatial distribution of lighton the diffuser, the lens array 174 may be configured to account for thethickness of the interference filter substrate, such that the apertureplane of the lens of the array is one or more of near, adjacent orcoincides with the plane of the diffuser The entrance pupil defined withaperture plane may comprise a virtual plane that coincides with theplane of the diffuser, for example with a lens comprising a plurality ofcomponents such as a multicomponent lens. The aperture plane can bephysically located between each of a plurality of lens components suchthat the entrance pupil of the lens coincides with the plane of thediffuser, for example. Alternatively or in combination, the substrate ofthe filter may comprise a diffusing material such as an opal glass, forexample which can place the diffuser near to the aperture, for exampleadjacent or coinciding with the apertures.

Alternatively or in combination, to reduce the system's sensitivity tothe spatial distribution of light on the diffuser, the functions of thediffuser and filter may be combined. FIG. 18 shows a schematic diagramof an exemplary optical layout, comprising a filter assembly 300. Thefilter assembly 300 can comprise a diffuser 164 and a filter coatingcomprising the filter array 170 coupled to the diffuser. The diffuser164 may comprise any material well-known in the art to havelight-diffusing properties, such as opal glass, Spectralon™,Polytetrafluoroethylene (PTFE), sandblasted glass, and ground glass. Thediffuser 164 may comprise a diffusing layer deposited, coated, fused, orotherwise coupled to an optical substrate such as glass. An integratedoptical component such as the filter assembly 300 as shown in FIG. 18can simplify the design of the lens, as well as significantly reduce thedependence of detected intensity distributions of incident light onspatial variations of the light intensity in the diffuser plane.Further, combining the diffuser with an interference filter substratecan allow for using a thicker substrate, providing more durability tothe substrate against the stresses that can be related to theinterference filter coating process.

Referring again to FIG. 7 , a spectrometer 102 in accordance withembodiments may further comprise a bulk light filter 188, configured toblock at least a portion of visible radiation included in the incidentlight. The light filter 188 can comprise, for example, an infraredhigh-pass filter (e.g., Hoya R72 bulk filter glass). Bulk filter 188 canimprove the function of each filter in the filter array 170, by blockingout those wavelengths that are undesirable for all channels, such aswavelengths that are outside the operational range of the spectrometer.Such wavelengths can produce undesirable stray light, since thewavelengths may not be effectively blocked by the interference filtersof the filter array 170.

To further simplify the design and production of the spectrometer, abulk visible light filter, such as light filter 188 of FIG. 7 , may becombined with a diffuser and/or an optical filter such as aninterference filter, to form an integrated filter assembly that providesone or more of bulk visible light filtering, diffusing, and/or opticalfiltering. For example, a thin layer of diffuser (e.g., opal coating)may be deposited, coated, fused, or otherwise coupled to an opticalsubstrate comprising a bulk light filter (e.g., colored glass),configured to block at least a portion of the incident light spectrum,and an optical filter configured to pass only a narrow band of thespectrometer's spectrum may also be deposited or coated on the diffuserlayer. Such a design, integrating the functions of a visible lightfilter, diffuser, and/or interference filter into one component, canreduce the total cost of production and the size of the spectrometer.Further, combining the bulk light filter with the interference filtercoating can also be advantageous in the design of interference filtersin a filter array. A filter array can be configured such that eachfilter in the array comprises a bulk filtering substrate that isspecifically configured based on the passband of the filter. Such aconfiguration can allow the use of a narrower passband for theindividual filters of the filter array, thereby improving theperformance of the interference filters (e.g., via better passbandtransmission, narrower passband) and reducing the cost of production.Furthermore, the use of individual bulk light filters as substrates forfilters of a filter array can reduce the number of interference filterlayers needed, thereby reducing the stress generated on the substrateduring the coating process. Reduced stress during the coating processcan, in turn, potentially allow the use of a thinner substrate and hencereduce the cost of dicing the substrate and provide improved reliabilitywith decreased weight.

FIGS. 19A-19F illustrate exemplary configurations of a filter assembly300 suitable for incorporation with a compact spectrometer as describedherein. A filter assembly may comprise a combination of two or moreoptical elements selected from an optical substrate 305, a diffusinglayer 310, and an optical filter 315. The optical substrate 305 maycomprise one or more of many optically transmissive materials such asone or more of glass, colored glass, sapphire, quartz, plastic, orpolycarbonate, for example. The diffusing layer 310 may comprise adiffuser 164 as described herein, such as cosine diffuser having anoutput intensity invariant with input angle. The optical filter 315 maycomprise a filter array 170 as described herein, comprising a pluralityof optical filters configured to transmit a specific wavelength band,based on the incidence angle of the light. The bulk light filter 320 maycomprise a visible light filter 188 as described herein, for example.

FIG. 19A illustrates a filter assembly 300 a, comprising an interferencefilter 315 coated on an optical substrate 300 comprising clear glass325.

FIG. 19B illustrates a filter assembly 300 b, comprising an interferencefilter 315 coated on of a diffusing layer 310 deposited, coated, fused,or otherwise coupled to an optical substrate 305 comprising clear glass325.

FIG. 19C illustrates a filter assembly 300 c, comprising an interferencefilter 315 coated on one side of an optical substrate 305 comprisingclear glass 325, the clear glass substrate comprising a diffusing layer310 deposited, coated, fused, or otherwise coupled to the opposite sideof the clear glass substrate.

FIG. 19D illustrates a filter assembly 300 d, comprising an interferencefilter 315 coated on one side of an optical substrate 305 comprising abulk light filter 320 (e.g., colored glass).

FIG. 19E illustrates a filter assembly 300 e, comprising an interferencefilter 315 coated on one side of the optical substrate 305 comprising abulk light filter 320, the bulk light filter comprising a diffusinglayer 315 deposited, coated, fused, or otherwise coupled to the oppositeside of the bulk light filter.

FIG. 19F illustrates a filter assembly 300 f, comprising an interferencefilter 305 coated on top of a diffusing layer 310 deposited, coated,fused, or otherwise coupled to one side of an optical substrate 305comprising a bulk light filter 320.

The optical elements shown in the configurations of FIGS. 19A-19F may becombined using any suitable method, or in any suitable order ororientation.

In configurations with an optical component comprising an interferencefilter coated on a substrate with a diffuser, such as the configurationsshown in FIGS. 19B, 19C, 19E, and 19F, testing of filter performance canbe designed in a way that takes the diffuser into account. In testingthe performance of interference filters combined with a diffuser,providing input light to the diffuser side may make the testingprocedure less than ideal, since the diffuse light incident on thefilters will generally hit the filters at many different angles. In sucha configurations, an incident angle-independent detection system (suchas the spectrometer described herein) may be provided to accuratelydetermine the output of the filters. A filter testing procedure can bedesigned such that light is provided to the filter-coated side instead,such that the light passes first through the filters and subsequentlythrough the diffuser, for example light having a controlled angle ofincidence on the filter such as collimated light. A commerciallyavailable spectrometer comprising a detector may be placed on the otherside of the filter assembly to measure the intensity and spectrum of thetransmitted light. Alternatively or in combination, light of acontrolled wavelength such as light from a grating can be transmittedonto the filter and the light energy of a specific narrow band ofwavelengths measured with a detector such as a photodiode for each of aplurality of wavelengths in order to determine the optical transmissionprofile of the filter as described herein.

The surface of the substrate supporting the filter coating may comprisean optically flat surface. As used herein an optically flat surfaceencompasses having a wavelength to root mean square (RMS) ratio that issurface sufficiently small, such as having an RMS of no more than one ormore of lambda (λ) over 5 (λ/5), lambda (λ) over 10 (λ/10), for example.The specified wavelength lambda (λ) may comprise one or more of theshortest wavelength measured with the spectrometer, longest wavelengthmeasured with the spectrometer, or an average wavelength measured withthe spectrometer.

Each of the components shown in FIGS. 19A to 19E may comprise singlepiece optical components. Each of the single piece optical componentsmay comprise one or more of a filter deposited on the substrate or adiffuser deposited on a substrate, and combinations thereof. One or moresingle piece optical components can be assembled with one or more othercomponents as described herein to assemble the spectrometer.Alternatively or in combination, a lens can be formed on the substrate,the lens comprising one or more of a geometric lens with a curvedsurface, a diffractive lens with echelettes formed on the substratesurface, a lens lithographically formed on the substrate, a Fresnellens, or a gradient index lens, and combinations thereof, for example.

FIG. 20 shows a schematic drawing of a cross-section of an exemplaryspectrometer module 160 as described, comprising an array 330 of filterassemblies 300. The cross-section shows two channels 177 of the support176 configured to support the array 330, each channel configured todirect light transmitted through each filter assembly 300 towards thedetector 190 as described herein. The support 176 can comprise aplurality of shoulders 181 configured to support the filter assemblies300. Each filter assembly 300 comprises an optical substrate 305 and anoptical filter 315 coupled to one side of the optical substrate. Theoptical substrate can be simple glass or a bulk light filter, such as aninfrared (IR)-pass filter glass. An aperture array 172 comprising aplurality of apertures 194 is located on top of the array of filters315, and a diffuser 310 is located on top of the aperture array 172. Alens 335 is coupled to each filter assembly 300 on the side of thesubstrate 305 opposite the side coated with the filter 315.

The lenses 335 can be an array of refractive lithographic lenses grownat the uncoated side of the substrate before the substrate is cut intoindividual filter assemblies. Alternatively or in combination, thelenses can be an array of Fresnel lenses, either etched into the opticalsubstrate before the substrate is cut into individual filter assemblies,or built separately from a thin plate, adhered to the optical substrate,and cut together with the substrate into individual filter assemblies,as in wafer level packaging techniques. Other methods may be used forbuilding lenses onto the optical substrate, as known in the art. Forexample, techniques commonly used in the optical wafer-level industry,such as using drops of glue with well controlled volumes to build thelenses, may be used. The lenses can be configured such that the diffuseris placed at the entrance pupil defined with aperture plane of the lens.

Lenses that are attached to or built directly onto the filter substrateare not limited to the configuration of FIG. 20 , and may beincorporated with one or more spectrometer module components andarrangements as described herein. The interference filter can beconfigured to account for the index of refraction of the lens that isattached to or formed on the substrate. Transmission properties of theinterference filter supported with the substrate comprising the lens canchange in relation to the index of refraction of the substrate, and theinterference filter can be configured in response to the index ofrefraction of the substrate supporting the filter such as aninterference filter, for example.

The aperture array 172 as shown in FIG. 20 is configured to restrict theamount of light passing through the filters 315 to areas of the filtersthat are functional for the collection of light by the lens 335corresponding to each channel 177. Such a configuration can suppress thecontribution of stray light to detected light intensity. The size ofeach aperture 194 of the aperture array may be configured to collect asmuch light as possible while inhibiting stray light transmission amongthe aperture channels, in order to increase the signal-to-noise ratio ofthe spectrometer system as described herein and with reference to FIGS.16B and 20 , for example. The aperture array may comprise a plurality ofapertures having a uniform cross-sectional size, a plurality ofapertures having a plurality of different cross-sectional sizes, or acombination thereof. Apertures having a plurality of differentcross-sectional sizes may comprise, for example, circular apertures ofdifferent diameters, or apertures having any other shape (e.g., starshape) to control the aperture area while keeping the aberrations in thedifferent channels similar.

An aperture array comprising a plurality of apertures having differentsizes can be advantageous in controlling the balance between theintensities of light collected by the different channels in the filterarray. Different channels of the filter array may provide light to thefilter array with different throughput, due to factors such as theillumination spectrum intensity, image sensor spectral response curve,and spectrometer system geometry. The balancing of the spectralillumination intensity with the transmission efficiency of the filterscan provide a more uniform amount of intensity on the detector elementsfor an object with a uniform spectral response, e.g. white, in order toincrease the signal to noise ratio of the spectrometer. A channel withone or more of a relatively lower light intensity or a relatively lowertransmission efficiency may be provided with an aperture of a relativelylarger size, such that the intensity of the illumination of the detectorcan be increased. A channel with one or more of a relatively higherlight intensity or a relatively higher transmission efficiency may beprovided with an aperture of a relatively smaller size, such that theintensity of the illumination on the detector array can be decreased.This balancing of the intensities of different channels using aperturesof different sizes, the light intensity detected by the lower opticalthroughput channels may be increased without saturating the signaldetected by the higher-efficiency channels. The light intensity detectedby the relatively higher optical throughput channels may be decreasedwithout decreasing the signal detected by the relatively lower opticalthroughput channels. Balancing the intensities of different channels canalso help to balance cross-channel disturbances, so that disturbances orcross-talk between the different channels can be better compensated.

Modulated Light Beam

When performing spectroscopy in ambient lighting conditions, thereduction of noise, such as that from ambient light impingent on thedetector can be helpful. An approach suitable for reduction of noise isto record a “dark frame,” comprising a signal taken with the opticalbeam turned off, in addition to a “probe frame,” comprising an signaltaken with the optical beam turned on. The dark frame represents arecording of the portion of the signal illumination that is due toexternal sources, such as ambient light. By subtracting the dark framefrom the probe frame, a signal showing the net effect of the opticalbeam can be isolated.

This approach can reduce noise but may not account for changes inambient light intensity or pattern over time in some instances. Forexample, if a probe frame is recorded followed by a dark frame, the darkframe is supposed to represent the ambient light at the time the probeframe was taken, but is a measurement of the ambient light some timelater. If the ambient light changed in intensity or pattern during thattime, the dark frame will fail to properly account for it, resulting ina higher level of noise.

In some examples, to account for the possibility of changes in ambientlighting and other sources of noise, more than one dark frame may berecorded. For example, two dark frames may be recorded, one before andone after a probe frame. The average of the two dark frames will then bea more accurate approximation of the “true” dark frame that would havebeen recorded during the probe frame, had the probe light not beenturned on. In further examples, a plurality of dark frames may berecorded and used to determine a trend in ambient noise, for example byfitting with a polynomial curve or other suitable function. While thismethod of noise reduction will typically lead to greater accuracy withgreater number of dark frames, it also may lead to inefficient amountsof data acquisition and processing.

Modulation effects of the light beam can be used to filter out noisefrom ambient sources. By modulating the probe beam at a known frequency,then demodulating the recorded signal using the same frequency as areference, noise can be reduced. However, the choice of modulationfrequency is helpful. Noise sources that vary at frequencies close to orthe same as the chosen modulation frequency may provide less than idealresults. Thus, if a modulation frequency is chosen that matches thecharacteristic frequency of some ambient source, demodulation may failto effectively eliminate that noise.

FIG. 21 shows an exemplary noise spectrum 2100 that may be the result ofambient light as measured by a detector apparatus. The curve 2101demonstrates a characteristic 1/f noise curve 2102, and which may be dueto ambient light changes as well as intrinsic noise sources in thedevice. Also illustrated are noise peaks 2103 and 2104 at 100 Hz and 120Hz. These peaks may be due to flicker at those frequencies, from lightsources such as fluorescent or incandescent lighting, for example.Choosing a modulation frequency near either peak 2103 or 2104 willresult in a noisier signal, as will choosing low modulation frequencysubject to 1/f noise 2102. The spectrometer circuitry as disclosedherein can be configured to emit a modulation frequency 2105 thatdecreases overlap with noise peaks. The light beam modulation can beconfigured in response to the available sensor frame rate.

The light source may be configured to provide the modulated optical beamincident on the sample with an illuminance (E_(v)) of no more than about100,000 lux (lm/m²), or within a range from about 20 lux (lm/m²) toabout 100,000 lux (lm/m²). The light source may be configured to providethe modulated optical beam incident on the sample with an irradiance ofno more than about 100 mW/cm², or within a range from about 0.1 mW/cm²to about 100 mW/cm².

FIG. 22 illustrates a method 2200 of measuring a spectrum, by whichfrequencies may be used to inhibit one or more of ambient noise,intrinsic noise, or other sources of noise. In some method 2200 may beperformed automatically by a processor associated with a computerreadable memory, and coupled to the spectrometer with communicationcircuitry. In some cases, method 2200 may be performed as calibrationstep to select modulation frequencies for future use, and in some casesmethod 2200 may be performed during operation to determine modulationfrequencies based on ambient conditions in use.

In step 2201, a noise spectrum is determined. This determination may bemade by performing a Fourier transform on a plurality of sequential darkframes. An FFT may be used to generate a noise spectrum in this manner.The frequency resolution of this measurement will be proportional to thenumber of frames used to generate it; for this reason, it may be desiredto record a large number of frames. The noise spectrum may in some casesidentify pixel-by-pixel noise spectra, and may in some cases identifynoise spectra averaged over a plurality of pixels, including for exampleall pixels. Further implementations may record data at only a smallnumber of pixels to increase the speed at which frames may be recorded.Alternatively or in combination, the ambient noise spectrum may begenerated using measurements from an independent sensor. The noisespectrum generated by step 2201 may relate measured noise as a functionof frequency, for example as depicted in FIG. 21 . The sensor data canbe transmitted to a remote server and the noise determined and processedwith the spectral data remotely, for example. The modulation of themeasurement beam can be performed in response to instructions from theremote server, for example. Alternatively, the modulation of themeasurement beam may comprise preset instructions to avoid sources ofnoise as disclosed herein.

In step 2202, one or more frequency bands are identified in which noiseis relatively low. These bands may correspond to local minima in thenoise spectrum, as can be found for example by a peak finding algorithm.In some cases, the frequency bands may be identified by finding localmaxima in the measured noise, then choosing frequencies that are atleast a minimum desired distance away from the noise maxima in order tosubstantially decrease noise. In many cases, it may be preferred tochoose a frequency high enough to avoid 1/f noise, and this may beaccomplished in many ways, such as designating a band of low frequenciesas undesirable, or by weighting a plurality of candidate frequency bandsto favor those at higher frequencies. In some cases, certain frequenciesmay be pre-designated as undesirable; for example, frequencies nearcertain multiples of 50 or 60 Hz may be designated as undesirable toavoid electronic or light noise due to AC power sources.

In step 2203, a modulation frequency is chosen from one of theidentified bands. This choice may be made on a variety of bases, such aschoosing the global minimum of noise, or choosing the maximum distancefrom noise maxima, or choosing among a set of local minima, for example.The chosen frequency may further comprise a set of chosen frequencies,which may be useful, for example, when multiple light sources are to bemodulated at different frequencies. When choosing more than onefrequency, the chosen frequencies may be selected from a set offrequencies within one band, of from more than one band, and thedifferences in frequencies may be adjusted to improve accuracy in futuredemodulation.

In step 2204, the chosen frequencies are assigned to be used inmodulation. This assignment may be performed automatically by setting avariable modulation frequency to a chosen frequency, and may in somecases involve an optional user confirmation. This step may also beperformed by defining a fixed set of frequencies for future use, forexample in the process of manufacturing the spectrometer.

In step 2205, the one or more chosen frequencies are used to modulateone or more light sources, for example, in Frequency DivisionModulation. By recording images or other sensor data taken during lightmodulation, then demodulating the recorded data, detected signals may beretrieved, allowing each light source to be identified by itscorresponding frequency. When multiple different light sources are used,such as a plurality of LEDs, each light source may be modulated at adifferent frequency. In some cases, the different frequencies may beselected from separate bands, and in some cases one or more frequenciesmay be selected from the same band.

In step 2206, the user directs the spectrometer at a sample. This allowsthe modulated light sources to illuminate the sample.

In step 2207, the user directs the detector of the spectrometer to viewthe illuminated sample. This step may include the user confirming thatthe modulated light sources are illuminating the correct portion of thesample, as well as confirming that the sample is within the field ofview of the detector.

In step 2208, the spectrometer records signals such as images to measurethe light scattered from the sample. In some cases, this measurementwill comprise a plurality of signals. Data representing these signalsmay be stored in memory for processing, processed on-the-fly, orprocessed remotely as described herein.

In step 2209, the associated processor processes the measured light.This step may include one or more demodulation steps for each modulationfrequency, to recover a spectrum corresponding to each modulated lightsource while eliminating noise. This may alternatively or additionallyinclude a step of subtracting a recorded dark frame, or a combination ofmultiple dark frames, from one or more recorded signals. This stepallows the isolation of one or more signals corresponding to one or morelight frequencies.

In step 2210, one or more spectra are determined from the signalsisolated in step 2209. These spectra may correspond to measured powersat one or more frequencies of emitted and/or scattered light. In somecases, the spectra may be corrected for the relative strengths ofdifferent illuminating beams; for example, the amplitudes correspondingto each of a plurality of light sources may be divided by theintensities of each respective light source, then combined to create anormalized spectrum.

Another method of modulation that may alternatively or additionally beemployed involves spatial recording of modulation data. In sensors suchas CMOS sensors comprising a rolling shutter architecture, the rollingshutter may be exploited to allow modulation at frequencies much higherthan the sensor frame rate. Because a rolling shutter exposes differentpixel columns to incident light at different times, a single frame suchas an image frame may comprise a spatial encoding of time information.

Each pixel column may then be treated as an independent framemeasurement, separated by an amount of time given by the rate at whichthe shutter exposes pixels. A spatial Fourier transform along thedirection of shutter movement may then be used to extract frequencyinformation, giving a column of frequency spectra, one for each row ofpixels. When performed on one or more dark frames, this sequence ofmeasurements may then be used in conjunction with method 2200 to achievea noise spectrum at higher frequencies and/or with fewer framesrecorded. Similarly, use of a rolling shutter in conjunction with aprobe beam may allow spectroscopy to be performed with high modulationfrequency, due to the high effective frame rate. Because rolling shuttermeasurements encode temporal data spatially, light with substantialspatial inhomogeneity may give rise in some cases to false frequencymeasurements. For this reason, rolling shutter measurements is mostuseful in situations where incident light is more spatially uniform.

Support Array

Referring again to FIGS. 7-9 and 16A-B, a compact spectrometer asdescribed herein may comprise a plurality of optical channels 177, eachchannel corresponding to a filter of a filter array 170, a lens of alens array 174, and a sensor area of an image sensor 190. A supportarray 176, comprising the plurality of optical channels, can be placedbetween the lens array and the image sensor to provide the correctseparation distance between the lens array and the image sensor, and toprevent stray light from entering or exiting each channel, as describedherein. As best seen in FIGS. 8 and 9 , each channel 177 of the supportarray 176 can be defined by a first opening 1771 adjacent the lensarray, a second opening 1772 adjacent the image sensor, and a channelwall 179 extending between the first opening and the second opening.Each channel can provide a controlled light path from the lens to thesensor, wherein the channel wall may be configured to absorb light(e.g., via black coating) such that light does not pass between channelsor reflect back from the wall into the channel. Light exiting from thesecond opening of each channel can reach a sensor area, wherein thesensor area may comprise one or more sensor elements configured todetect the light exiting the channel.

The spectrometer can be configured to inhibit cross-talk. Referringagain to FIGS. 7-9 and 16A-B, a channel 177 may extend from the lensarray 174 to a stopper mounting 178, wherein the stopper mountingsecures the support array 176 to the image sensor 190. In thisconfiguration, the second opening 1772 of each optical channel isseparated from the image sensor by a distance substantiallycorresponding to the thickness of the stopper mounting, such that thewall each channel does not extend all the way to the image sensor.Consequently, light exiting from the second opening of a channel may notonly reach the sensor area corresponding to the channel, but may also“crosstalk” or reach into one or more adjacent sensor areascorresponding to one or more neighboring channels. The extent of thecrosstalk between adjacent channels may be controlled by controlling thedistance between the channels and the image sensor, for example byvarying the thickness of the stopper mounting.

FIG. 23 schematically illustrates the crosstalk between channelsdetected by an image sensor as described herein. The image sensor 190can comprise a plurality of sensor areas 1901 configured to detect lightarriving at the image sensor through the plurality of channels formed bythe support array. Each sensor area 1901 can comprise an imaging portion1902 comprising the sensor elements from which data is collected. Asshown in FIG. 23 , the imaging portion can have a round or substantiallycircular shape, to match a round or substantially circular shape of thesecond opening of the channel facing the image sensor. Light exitingfrom the second opening of each channel may hit the image sensor in apattern 1903, whose area can depend on the distance between the secondopening of the channel and the image sensor area. As this distance isincreased, the area of the pattern of light incident on the image sensorcan increase. As this distance approaches zero, the area of the patternof light incident on the image sensor can approach the area of thesecond opening of the channel. The distance between the second channelopening and the image sensor may be adjusted and configured such thatlight exiting from one channel hits the image sensor with a pattern 1903that does not overlap with the imaging portions of sensor areascorresponding to neighboring channels, as shown in FIG. 23 . In such aconfiguration, even though there is some crosstalk at the image sensorbetween adjacent sensor areas corresponding to neighboring channels,this crosstalk is limited to non-imaging portions 1904 of the imagesensor, disposed about the periphery of the imaging portions. Thenon-imaging portion 1904 may comprise a portion of the sensor array fromwhich sampled pixels are excluded from the analysis of the spectraldata. Since the stray light from adjacent channels does not encroach theimaging portion that forms the image of the detected light from onechannel, interference among signals detected from different sensor areasof the image sensor can be inhibited, for example minimized.

In the example shown in FIG. 23 , the image sensor 190 may have a lengthwithin a range from about 3-6 mm, for example about 4.8 mm, and a widthwithin a range from about 2 mm to about 4 mm, for example about 3.6 mm.The image sensor may comprise an array of 12 sensor areas 1901, eachhaving a circular, central imaging portion 1902 with a diameter of about0.8 mm. Each imaging portion may be separated from an adjacent imagingportion a distance within a range from about 0.3 to about 1 mm, forexample about 0.8 mm. The distance between the second openings of thechannels and the image sensor may then be configured such that lightexiting from the second opening of a channel hits the image sensor in acircular pattern 1903 having a diameter of about 1.6 mm. In this way,the pattern of light from one channel incident on a sensor area maycross over into only non-imaging portions of adjacent sensor areas.

Increasing the area of the imaging portion of each sensor area can haveimportant advantages for a compact spectrometer as described herein. Forexample, larger imaging portions can allow light of higher angles ofincidence to be detected by the image sensor, thus extending thespectral range covered by each optical channel. However, inconfigurations as described wherein the channel walls do not extend allthe way to the image sensor, the size of each imaging portion of asensor area can be limited by the crosstalk between channels. Forexample, in the configuration shown in FIG. 23 , increasing the area ofthe imaging portion 1902 of each sensor area 1901 would result in theincrease in interference among signals detected from different sensorareas of the image sensor, due to the crosstalk between adjacent sensorareas.

To increase the area of imaging portions of an image sensor withoutincreasing crosstalk between optical channels, a support array may beconfigured such that the channel walls extend all the way to the imagesensor. FIG. 24A shows a cross-sectional view of an optical subassemblycomprising an exemplary embodiment of a support array. The opticalsubassembly 165 a comprises a filter matrix 170, aperture array 172,lens array 174, and image sensor 190 as described herein. The opticalsubassembly further comprises a support array 176 a having a pluralityof optical channels 177 a, each optical channel defined by a firstopening 1771 a adjacent the lens array, a second opening 1772 a adjacentthe image sensor, and a channel wall 179 a extending between the firstopening and the second opening. As shown, the channel walls can extendall the way to the image sensor, such that each channel is opticallyisolated from other channels through the entire light path from the lensarray to the image sensor. In this configuration, light exiting eachchannel from the second opening 1772 a directly hits the correspondingsensor area of the image sensor, such that the pattern of light incidenton the sensor area can substantially correspond to and match the sizeand shape of the second opening of the channel. FIG. 24B schematicallyillustrates the light pattern detected by the image sensor for thesupport array configuration of FIG. 24A. As shown, the pattern 1903 a oflight incident on each sensor area 1901 of the image sensor 190 does notoverlap with the patterns of light incident on adjacent sensor areas.Thus, the imaging portion 1902 a of each sensor area can be increased insize to substantially overlap with the area of the pattern of lightincident on each sensor area, and the area of non-imaging portions 1904a of the image sensor can be substantially reduced.

Alternatively to or in combination with extending the channel walls allthe way to the image sensor, a support array may be modified in shape tofurther increase the size of the imaging portions of the image sensor.As described herein, each channel of a support array may comprise afirst opening adjacent the lens array, a second opening adjacent theimage sensor, and a channel wall extending between the first opening andthe second opening. Both the first opening 1771 and the second opening1772 of each channel 177 may be round or substantially circular inshape, thereby defining a substantially cylindrical channeltherebetween, for example as shown with reference FIGS. 8-9 . In manyembodiments, the first opening adjacent the lens array can be round inorder to provide an aperture stop to control the optical performance ofthe system. The second opening adjacent the image sensor may have anyshape, which can be optimized to maximize the area of the imagingportions at the image sensor.

FIGS. 25A-C illustrate an exemplary examples of a support arraycomprising channels having rectangular openings facing the image sensor,for example square-shaped openings facing the image sensor. FIG. 25Ashows a sectional view; FIG. 25B shows a top view; and FIG. 25C shows abottom view of the support array 176 b. The support array 176 bcomprises a plurality of channels 177 b each defined by a first opening1771 b facing the lens array, a second opening 1772 b facing the imagesensor, and a channel wall 179 b extending between the first opening andthe second opening. As illustrated in FIG. 25B showing the top view ofthe support array 176 b, wherein the top view comprises the view fromthe lens array side, the first opening 1771 b may have a round shape toprovide an aperture stop at the lens. As shown in FIG. 25C showing thebottom view of the support array 176 b, wherein the bottom viewcomprises the view from the image sensor side, the second opening 1772 bmay have a rectangular or substantially square shape, for example.Accordingly, the channel walls 179 b may transition from a round shapeto a rectangular or square shape over the length of the channel.

FIG. 25D schematically illustrates the light pattern detected by theimage sensor for the support array configuration of FIGS. 25A-C. Lightexiting from the square-shaped second openings of the channels cancreate substantially a square-shaped pattern 1902 b of light on eachsensor area 1901 the image sensor 190. Accordingly, the image sensor canbe configured to have square-shaped imaging portions 1903 b to detectthe intensity of the incident light having the square-shaped patterns. Asquare-shaped imaging portion can have a larger area compared to around-shaped imaging portion of an image sensor having approximately thesame size and number of sensor areas (such as imaging portion 1902 a ofFIG. 24B). The square images thus created on the image sensor canprovide additional information compared to round images created byround-shaped imaging portions, for example at the corners of the squareimages. This additional information can increase the spectral range oflight detected at each sensor area, since the additional area of thesquare-shaped imaging portions can capture incident light with higherangles of incidence. In embodiments wherein the channel walls extend allthe way to the image sensor, the square-shaped pattern of light incidenton the image sensor can have an area that is similar to the area of thesecond opening of the channel, such that the pattern of light on eachsensor area does not overlap with the patterns of light incident onadjacent sensor areas. Thus, the imaging portion 1903 b of each sensorarea can be increased in size to substantially overlap with the area ofthe pattern of light incident on each sensor area, and the area ofnon-imaging portions 1904 b of the image sensor can be substantiallyreduced.

While the spectrometer can be configured in many ways, the filter andlens array as described herein can be configured to provide an annularspectral pattern 2500 on each rectangular sensor area. For example, thefilters many comprise interference filters with coatings or etalons andcombinations thereof. The annular spectral pattern may comprise annularvariations in intensity 2510 corresponding to spectral lines of thespectrum from the object. The annular patterns may comprise segments2520 extending into the corner portions of imaging portion 1903 b ofeach sensor area. These annular segments provide additional spectraldata and information that can increase the resolution of thespectrometer. The processor coupled to the detector can be configured toreceive the spectral data from the corner portions. The processor asdescribed herein can be configured to measure the spectrum of the objectin response to the annular segments extending into the corner portionsof the imaging portions. The processor may comprise a remote processorsuch as a cloud based server, for example.

FIG. 26 shows an oblique view of an exemplary optical module assembly ofa compact spectrometer. The optical module assembly 2600 comprises aspectrometer head 120 and a control board 105 as described herein,wherein the spectrometer head is configured to measure a samplematerial, and the circuit board is configured to receive data from thespectrometer head and transmit, store, and/or analyze the data. Thespectrometer head comprises a spectrometer module 160 and anillumination module 140, and may optionally comprise a sensor module 130as described herein. For example, the spectrometer module may comprise afilter matrix, lens array, and a 2-dimensional image sensor as describedherein, wherein the lens array may be coupled to the image sensor via asupport array comprising a plurality of channels having round-shapedopenings facing the lens array and square-shaped openings facing theimage sensor, as described herein. The data generated the imagingportions of the image sensor may be transmitted to the circuit board forprocessing. The control board 105 may comprise circuitry to process thesignal from the sensor as described herein. A flex circuit board mayextend from the spectrometer head 120 to the control board 105. Asupport comprising an extension can extend between the spectrometer headand control circuitry. Alternatively or in combination, the processorcircuitry can be mounted on the flex printed circuit board, for example.

Lateral Diffuser

Referring again to FIG. 1A, in some cases, light emanating from a sampleS can reach the input port of the spectrometer module 160 (e.g.,spectrometer window 162) such that the sample light is distributedevenly or unevenly across the front surface of the input port. Thesample light may include light originated from the integrated lightsource of the spectrometer (e.g., at least a portion of the optical beam10 generated by the illumination module 140 that is reflected back bythe sample), and/or light originated from the environment (e.g., ambientlight). The light that is originated from the integrated light sourceand reflected from the measured sample may be affected by variousgeometrical deviations related to the measured sample and/orconfigurations of the spectrometer. For example, the geometricaldeviation may comprise uneven light distribution across the surface ofthe spectrometer input port, or different angles of incidence of thesample light with respect to the surface of the input port.

Sources of geometrical deviations may include, for example: 1)Differences in distances between various portions of the sample and theintegrated light source of the spectrometer, combined with differencesin distances between the illuminated portions of the sample anddifferent locations of the spectrometer input port (differences indistances between various portions of the sample and the light sourcelead to uneven illumination of the sample surface, especially as thedistance between the sample surface and the light source decreases;differences in distances between illuminated portions of the sample andthe spectrometer input port leads to uneven distribution of input lightintensity across the input port, especially as the distance between thesample surface and the light source decreases); 2) Uneven reflection oflight from sample may cause uneven spread of light across the frontsurface of the spectrometer input port; 3) Measuring a sample whileholding the spectrometer tilted with respect to the sample surface; 4)Dirt and particles on the outside surface of the spectrometer inputport, blocking some of the incoming light with a non-uniform geometricaldistribution; 5) Uneven illumination when using the device with variousaccessories. One or more of these reasons, in addition to various otherreasons not listed, may result in geometrical deviations of lightincident on the spectrometer input port.

Disclosed herein are methods and devices for spatially spreading theincoming sample light before the light reaches the optical detector ofthe spectrometer, to improve the uniformity of the spatial distributionof light on the detector. For example, the methods and devices canspatially distribute the light from the sample substantially evenlyacross a front surface of the spectrometer configured to receive thelight, such as across a lateral dimension of a filter array. Thesubstantially even spatial distribution of light can be uniform acrossthe front surface of the spectrometer to within about 25%, or to withinabout 10%. For example, light can be distributed substantially evenacross a lateral dimension of the filter array such that the lighttransmitted to each filter of the filter array can be substantiallyhomogenous with respect to the spatial distribution profile. Thesemethods and devices may be incorporated with any embodiment of a compactspectrometer as described herein.

FIGS. 27A and 27B schematically illustrate the lateral distribution oflight transmitted through one or more cosine diffusers 2700. In somecases, the spectrometer may comprise one or more cosine diffusersconfigured to receive the input light from the sample and transmitdiffuse light. For example, a single cosine diffuser may be placedadjacent to or may be attached to the front or back surface of thespectrometer input port (such as spectrometer window 162 shown in FIG.1A and FIG. 7 ), to spread the input light emanating from the samplebefore the light enters the spectrometer module. The cosine diffuser maycomprise a thin flat polymer, an engineered diffuser, or any other typeof diffuser known in the art, preferably having a Lambertiantransmittance function. FIG. 27A illustrates the configuration with asingle cosine diffuser 2700, wherein the incident light 200 from thesample impinges on front or outer input surface 2705 of the cosinediffuser that faces the sample. Light is transmitted through thediffuser such that diffuse output light 205 exits the diffuser from theback or inner output surface 2710 of the diffuser that faces away fromthe sample. For example, cosine diffuser 2700 may be equivalent to firstdiffuser 164 as shown in FIG. 7 , wherein light from the sample entersthe spectrometer module 160 through the spectrometer window 162 and istransmitted through the diffuser 164 to enter the light filter 188and/or remaining optical components of the spectrometer module. Asillustrated in FIG. 27A, the distribution of the transmitted diffuselight can be substantially Lambertian, such that the light is scatteredto all directions of the hemisphere above the output surface. An idealor perfect Lambertian diffuser would have a true cosine function output,wherein the incident light is scattered equally to all directions of thehemisphere on the side of the output surface 2710. However, existingLambertian diffusers typically do not have an ideal or perfectLambertian output due to one or more of many reasons. For example,depending on the diffusing properties of the diffuser, some of the inputlight may be transmitted through the diffuser without scattering, suchthat input light of a certain angle of incidence may translate to outputlight having a corresponding angle of transmission. Additionally, theoutput angles of the transmitted diffuse light may not have a truecosine distribution. Therefore, the distribution of output light fromthe diffuser may have a relatively higher intensity at small angles oftransmission (e.g., perpendicular to the diffuser surface), andrelatively lower intensity at large angles of transmission (e.g., 45°with respect to the normal to the diffuser surface).

FIG. 27B illustrates a configuration with two cosine diffusers 2700 aand 2700 b. Incorporating two or more cosine diffusers into thespectrometer can help reduce the variation in the lateral distributionof output light across a width 2715 of the diffuser, thereby providing amore laterally uniform distribution of diffuse output light. Forexample, as shown in FIG. 27B, the output light 205 a from the firstcosine diffuser 2700 a can be have a relatively narrow lateraldistribution that is focused about the location 2720 on the firstdiffuser where the incident light 200 impinges on the first diffuser.The diffuse output light 205 a from the first diffuser can subsequentlyenter the second diffuser 2700 b at various locations across the widthof the diffuser, such that the output light 205 b from the seconddiffuser can have a relatively wider lateral distribution.

Output light 205 b from the second diffuser can have an intensitydistribution that varies across the width or the area of the diffuser.For example, output light exiting the second diffuser at locationsrelatively farther from the location 2720 on which the incident light200 impinges on the first diffuser can have a relatively lower intensitycompared to output light exiting the diffuser at locations relativelycloser to the location 2720. To reduce this spatial variation in theintensity of output light, the separation distance 2717 between the twodiffusers can be increased. The spectrometer can be configured with twoor more diffusers that are separated by a distance 2717 that is greaterthan or substantially similar to a width of the desired light outputarea. For example, the two diffusers can be separated by a distance thatis approximately half of the output lateral dimension of the filterarray (e.g., half of the width of filter matrix 170 shown in FIG. 7 ;˜4-5 mm in some exemplary configurations), but greater than 3 times thelateral dimension of the lens aperture (e.g., diameter of an aperture194 of the aperture array 172, as shown in FIG. 9 ; ˜0.8 mm in someexemplary configurations). Greater separation distance between thediffusers can provide better uniformity in the intensity distribution ofthe output light. Greater separation distance between the diffusers canalso result in decreased overall intensity of the output light. Oneexemplary configuration of the first cosine diffuser 2700 a and secondcosine diffuser 2700 b in an optical stack is shown in FIG. 7 . Thefirst cosine diffuser 2700 a may correspond to the first diffuser 164,and the second cosine diffuser 2700 b may correspond to the seconddiffuser 166, wherein a light filter 188 or other optical component maybe disposed between the two cosine diffusers in the optical stack inorder to place the two diffusers at a desired separation distance. Thelight filter 188 or other optical component positioned between the twocosine diffusers may have a thickness that matches a desired separationdistance between the two diffusers to achieve a specific lateraldistribution profile.

The spectrometer can be configured with more than two cosine diffusers,such as three or more diffusers, arranged sequentially along the opticalpath of the light from the sample.

Alternatively or in addition to the cosine diffusers as shown in FIGS.27A-B, which can angularly distribute transmitted diffuse light in acosine manner, lateral diffusers configured to spatially distributelight in the lateral dimension can also be incorporated into thespectrometer. A lateral diffuser can be configured to receive inputlight having a first lateral distribution along a lateral dimension ofthe diffuser (e.g., width of the diffuser), and transmit output lighthaving a second lateral distribution that is greater than the firstlateral distribution. A lateral diffuser can have a greater thicknessand/or comprise microstructures configured to diffuse incoming lightlaterally across its width.

FIG. 27C illustrates an exemplary configuration of a lateral diffuser2750. The lateral diffuser 2750 may comprise a support material 2755 anda plurality of scattering structures 2760 disposed within the supportmaterial. The refractive index of the scattering structures may begreater than the refractive index of the support material surroundingthe scattering structures, in order to effectively scatter the lightthat impinges upon each scattering structure. For example, the supportmaterial may comprise a plurality of plates made from transparent resin,and the plurality of scattering structures may comprise a plurality ofparticles having a refractive index greater than the refractive index ofthe resin to efficiently scatter the incident light. Alternatively, thelateral diffuser may comprise a porous diffuser wherein the supportmaterial comprises polytetrafluoroethylene (PTFE/Teflon), polystyrene,or other diffusive material, and the plurality of scattering structurescomprises a plurality of pores. The plurality of scattering structuresmay be non-overlapping or partially overlapping.

The diffusivity of a lateral diffuser and hence the extent of lateraldistribution of input light exiting the lateral diffuser may becontrolled by varying one or more of the refractive index of thescattering structures, refractive index of the support material, thesize of the scattering structures, the number or density per unit volumeof the scattering structures, and the overall thickness of the diffuser.The thickness of the lateral diffuser and the size and density of theplurality of scattering structures may be arranged such that a majorityof light exiting the lateral diffuser is scattered by at least two lightscattering structures. One or more properties of the lateral diffusercan be controlled to configure the diffuser such that for input lighthaving any full-width half maximum (FWHM) value, the FWHM of the outputlight is in a range which is relatively large compared to the size ofeach optical channel or each filter of the filter array. For example, ina lateral diffuser having a thickness of about 100 um, comprisingscattering particles having a diameter of about 10 um at a particleconcentration of about 2.5%, assuming ideal scatter wherein the light isvery efficiently scattered in substantially all directions, input lightof any spot size may result in output light having a FWHM of at leastabout 0.3 mm.

In operation, the input light 200 incident on the input surface 2765 ofthe lateral diffuser hits one or more of the plurality of scatteringstructures as the light is transmitted through the diffuser. Thescattering structures can scatter the incident light in a plurality ofdirections, as shown in FIG. 27C, and the scattered light cansubsequently hit one or more additional scattering structures beforeexiting the diffuser from the output surface 2770. The input light caneventually exit the diffuser from the output surface 2770 at variouslocations along the width 2775 of the diffuser depending on theirdirection of scatter. Thus, the input light 200 impinging upon the inputsurface of the lateral diffuser at a first location 2780 along the widthof the diffuser can eventually exit the diffuser from the output surfaceat a plurality of locations along the width of the diffuser (e.g.,second location 2782, third location 2784, fourth location 2786, andfifth location 2788), such that the transmitted diffuse light isscattered along the lateral dimension (e.g., width of the diffuser).

For example, the input light can hit a first scattering structure 2760a, scattering the light in a first direction 201 a and in a seconddirection 201 b. The light scattered in the first direction 201 a cansubsequently hit a second scattering structure 2760 b, and lightscattered in the second direction 201 b can subsequently hit a thirdscattering structure 2760 c. Light impinging on the second scatteringstructure 2760 b can scatter in a plurality of directions and exit thediffuser from the output surface 2770 at the second location 2782 andthird location 2784 along the width of the lateral diffuser. Lightimpinging on the third scattering structure 2760 c can be furtherscattered in a first direction 202 a and a second direction 202 b. Thelight scattered in the first direction 202 a can hit a fourth scatteringstructure 2760 d, subsequently scatter in another direction to hit afifth scattering structure 2760 e, then exit the diffuser from theoutput surface 2770 at the fourth location 2786. The light scattered inthe second direction 202 b can hit a sixth scattering structure 2760 f,and subsequently scatter in another direction to exit the diffuser fromthe output surface at a fifth location 2788.

Examples of commercially available lateral diffusers and additionaldetails regarding the principle of operation of a lateral diffuser asherein described may be found on the Internet, for example, athttp://www.entire.com.tw/english/product1.htm (Entire Technology Co. LTDdiffuser plate) andhttp://www.chimeicorp.com/en-us/products/electronic-materials/optical-grade-diffuser-plate/(CHIMEIoptical grade diffuser plate).

Optionally, a lateral diffuser may also be a cosine diffuser, configuredto angularly distribute light according to a cosine function. In such acase, the same diffuser can both angularly and spatially distributeinput light, such that the profile of transmitted diffuse light issubstantially uniform both along a spatial or lateral dimension, as wellas in the angular dimension.

Referring again to FIG. 7 , the first diffuser 164 and/or the seconddiffuser 166 may comprise lateral diffusers, such as the lateraldiffuser shown in FIG. 27C, configured to spatially distribute the inputlight along the lateral dimension. The lateral distribution of light byone or more of these first and second diffusers can improve the spatialuniformity of the sample light that enters the filter matrix 170. Asdescribed herein with respect to FIG. 7 , diffusers 164 and 166 may alsobe cosine diffusers configured to angularly distribute light to generateoutput light having a substantially Lambertian distribution. Inconfigurations wherein at least one of these diffusers is also a lateraldiffuser, the thickness of the light filter 188 may be reduced, as lessseparation distance may be needed between the first and second diffusersto spatially distribute output light along the lateral dimension asdescribed in reference to FIG. 27B. Both the first and second diffusersmay be both cosine and lateral diffusers configured to distribute lightangularly and spatially, or one of the two diffusers may be cosinediffuser while the other may be a lateral diffuser. Alternatively, theconfiguration as shown in FIG. 7 may be modified to have only a singlediffuser that is both a cosine diffuser and a lateral diffuser. In sucha configuration, the thickness of the light filter 188 may besignificantly reduced as the light filter no longer needs to provide aseparation distance between two diffusers. Optionally, the light filter188 may be eliminated altogether, with one or more other opticalcomponents in the optical stack configured to provide thelight-filtering function performed by the filter 188. For example, thespectrometer window 162 or the filter matrix 170 may comprise a materialor coating configured to filter out wavelengths in the UV or visibleregion of the light spectrum.

One exemplary configuration of the first cosine diffuser 2700 a andsecond cosine diffuser 2700 b in an optical stack is shown in FIG. 7 .The first cosine diffuser 2700 a may correspond to the first diffuser164, and the second cosine diffuser 2700 b may correspond to the seconddiffuser 166, wherein a light filter 188 or other optical component maydisposed between the two cosine diffusers in the optical stack in orderto place the two diffusers at a desired separation distance. The lightfilter 188 or other optical component positioned between the two cosinediffusers may have a thickness that matches a desired separationdistance between the two diffusers to achieve a specific lateraldistribution profile.

Stray Light Reduction

FIG. 28 illustrates an exemplary configuration of an optical stack of afilter array-based spectrometer, and the passage of stray light throughthe optical stack to the detector. Optical stack 2800 can be a portionof a spectrometer module as described herein (such as spectrometermodule 160 as shown in FIG. 7 ). The optical stack 2800 may comprise adiffuser 2805, a filter array 2810 comprising a plurality of filters2812, an aperture array 2815 comprising a plurality of apertures 2817, alens array 2820 comprising a plurality of lenses 2822, a support array2825 comprising a plurality of channels 2827, and a detector or imagesensor 2830 comprising a plurality of sensor areas 2832. Each opticalcomponent can be similar in many aspects to a corresponding, similarlynamed optical component described elsewhere herein (e.g., diffusers 162and/or 166, light filter 188, filter matrix 170, aperture array 172,lens array 174, support array 176, detector 190, etc., as shown in FIG.7 ). The diffuser can be configured to receive light emanating from thesample being measured with the spectrometer, the filter array can beconfigured to receive the light transmitted through the diffuser, thelens array can be configured to receive the light transmitted throughthe filter array, and finally the image sensor can be configured toreceive the light transmitted through the lens array. The aperture arraycan be disposed between the diffuser and the lens array, such that thelight from the sample passes from the diffuser to the lens array throughthe apertures of the aperture array. The support array can be disposedbetween the lens array and the image sensor, such that the light passesfrom the lens array to the image sensor through the channels of thesupport array. The optical stack can comprise a plurality of opticalchannels 2835 corresponding to the plurality of filters, apertures,lenses, channels, and image sensor areas.

Diffuse light transmitted through the diffuser can enter the opticalstack at many angles. Light that enters the optical stack at largeangles with respect to the normal to the plane of the optical stack maybe reflected from one or more channel side walls defining the channelsof the support array, and reach the image sensor at unintended anglessuch that the light may be difficult to resolve spectrally.Alternatively or additionally, light entering the optical stack at largeangles may pass from one channel to an adjacent channel, causing mixingof light between different optical channels and consequently ambiguityin the spectral resolution of the input light. Arrow 2850 illustratesstray light caused by the reflection of light from the channel sidewalls 2829 of the support array. Arrow 2852 illustrates stray lightcaused by the passing of light between adjacent channels.

The spectrometer can be configured in one or more of many ways to reduceor eliminate the amount of stray light that reaches the image sensor.For example, the aperture array may comprise a first aperture arraylayer and a second aperture array layer configured to limit the anglesof light that can pass through the aperture array; the filter array maycomprise an opaque material disposed between adjacent filters; thechannel side walls of the support array may comprise micro featuresconfigured to redirect or absorb light having large angles; the supportarray may comprise channel bottom walls having a central openingstherethrough; the optical stack may comprise angle limiting layersconfigured to limit the angles of light that enter the optical stack,such as a micro-louver film or a prism film. Each of these elements orfeatures may be incorporated into a spectrometer as described hereinalone or in combination with one or more other elements or features, toachieve the desired reduction of stray light as well as improved lighttransmission efficiency.

Filter Array with Opaque Material, Aperture Array Comprising TwoAperture Array Layers

FIG. 29A illustrates an optical stack comprising two aperture arraylayers and an opaque material disposed between adjacent filters of thefilter array. Optical stack 2900 comprises a diffuser 2805, lens array2820, support array 2825, and image sensor 2830 as described inreference to FIG. 28 . The optical stack 2900 further comprises a filterarray 2910 including an optional opaque material 2914 disposed betweenadjacent filters 2912 of the filter array. The optical stack 2900further comprises an aperture layer 2915 comprising a first aperturearray layer 2960 and a second aperture array layer 2970. As shown, thefirst aperture array layer may be disposed between the diffuser and thefilter array, and the second aperture array layer may be disposedbetween the filter array and the lens array. The first aperture arraylayer comprises a first plurality of apertures 2962, and the secondaperture array layer comprises a second plurality of apertures 2972aligned with the first plurality of apertures.

The opaque material 2914 can comprise any material configured to preventcross-talk of light between adjacent filters of the filter array, suchas an opaque glue or coating configured to substantially absorb lightthat impinges upon the material. Arrow 2952 shows light entering theoptical stack at a large angle of incidence, such that the light, ifuninterrupted, would cross between two or more adjacent filters whiletraveling through the filter array. In the configuration of FIG. 29A,the light hits the opaque material disposed between two adjacentfilters, and is substantially absorbed by the opaque material. Thus, theopaque material can prevent light entering the optical stack at largeangles of incidence from reaching the image sensor. While FIG. 29A showsthe opaque material 2914 used in combination with the two aperture arraylayer configuration, the opaque material may also be used with any otherconfiguration of the optical stack, such as the single aperture arrayconfiguration shown in FIG. 28 .

The first and second aperture array layers can be arranged to blocklight entering the optical stack at an angle of incidence outside apredetermined range that is deemed acceptable for the normal operationof the spectrometer. Arrows 2950 a and 2950 b show light entering theoptical stack at the maximum angle of incidence 2954 allowed to passthrough the aperture array 2915. As illustrated in FIG. 29A, lightentering the optical stack at angles smaller than or equal to angle 2954do not hit the channel side walls 2829 of the support array beforereaching the image sensor. Thus, the double aperture array layerconfiguration can prevent the reflection of light from the channel sidewalls shown in FIG. 28 .

FIG. 29B schematically illustrates the passage of light through thefirst and second aperture array layers of FIG. 29A. A first aperture2962 of the first aperture array layer 2960 and a corresponding secondaperture 2972 of the second aperture array layer 2970 are aligned abouta common central axis 2917 of the first and second apertures. Arrows2950 a and 2950 b show light entering the optical stack at the maximumangle of incidence 2954 allowed to pass through the aperture array 2915.The first aperture can have a first diameter 2963 and the secondaperture can have a second diameter 2973, wherein the ratio between thefirst diameter and the second diameter may be adjusted to control themaximum angle of light allowed to pass through both apertures. Forexample, the first diameter may be greater than the second diameter, thesecond diameter may be greater than the first diameter, or the firstdiameter and the second diameter may be equal. The first and secondaperture arrays layers may separated by a separation distance 2919. Themaximum angle of incidence 2954 allowed to pass can be controlled byarranging the first and second aperture array layers according to thefollowing equation:

$\alpha = {\tan^{- 1}\frac{\frac{L}{2} + \frac{S}{2}}{D}}$wherein α is the maximum angle of incidence 2954 of light allowed topass through the aperture array, L is the first diameter 2963 of thefirst aperture, S is the second diameter 2973 of the second aperture,and D is the effective separation distance between the first and secondaperture array layers, or the free-space separation distance 2919divided by the refractive index of the medium. Thus, one or more of thefirst diameter, the second diameter, and the separation distance may beadjusted to achieve a predetermined, desired value of the maximum angleof incidence 2954. For example, to achieve a maximum allowed angle ofincidence of 40°, the first plurality of apertures can be configured tohave a first diameter of about 1 mm, the second plurality of aperturescan be configured to have a second diameter of about 0.68 mm, and thefirst and second aperture array layers can be disposed at a separationdistance of about 1 mm. In many cases, the predetermined range for theangles of incidence of input light allowed to pass through the aperturearray can be from about −40° to about 40° with respect to the normal tothe plane of the optical stack. Depending on the specific configurationof the optical stack, the predetermined range can be increased to awider range (e.g., from about −50° to about 50°), or decreased tonarrower range (e.g., from about −30° to about 30°).

Support Array Channel Side Walls Comprising Micro Features

FIG. 30A illustrates an exemplary configuration of a channel 2827 of asupport array (e.g., support array 2825 shown in FIG. 28 ). The channelmay have a frustum shape, such as the substantially frustoconical shapeshown in FIGS. 28 and 30A, wherein a top opening 3005 of the channel issmaller than a bottom opening 3010 of the channel. Light 3050 enteringthe channel through the top opening at an angle 3054 with respect to thenormal to the plane of the top opening that is outside a predeterminedrange of allowable angles may be reflected one or more times from thechannel side wall 3015 before exiting the channel through the bottomopening. For example, light entering the channel at an angle 3054 thatis greater than an angle 3020 (between a plane of the channel side wall3015 and the normal to the plane of the top opening) may be reflectedone or more times from the side wall. The side wall can be configured toreduce an intensity of light by at least about 90% after a singlereflection of the light from the side wall. For example, the side wallcan comprise a material or a coating configured to absorb at least about90% of light hitting the side wall.

FIGS. 30B and 30C illustrate horizontal cross-sections of exemplaryconfigurations of the channel of FIG. 30A. As shown in FIG. 30B, thechannel 2827 a can be defined by a continuous, rounded side wall 3016,such that the horizontal cross-section of the channel forms a circle. Inthis configuration, the light 3050 entering the channel at a large angletypically experiences a single reflection 3052 from the side wall beforeexiting the channel. Alternatively, the channel can be defined by two ormore side walls connected at an angle relative to one another. Forexample, as shown in FIG. 30C, the channel 2827 b can be defined bythree or more straight side walls 3017 connected at one or more anglesrelative to one another, such that the horizontal cross-section forms apolygon. The polygon can have the shape a five-point star as shown inFIG. 30C, or can be any other polygon comprising any number of sides. Inthis configuration, the light 3050 entering the channel at a large anglemay experience two or more reflections 3054, 3056 from two or more sidewalls before exiting the channel. Since each reflection of light from aside wall can result in the absorption of greater than 90% of the lightenergy by the side wall, each additional reflection of light cansignificantly reduce the total amount of reflected stray light. Forexample, assuming that the side walls 3017 of the channel 2827 b of FIG.30C absorb about 90% of the light hitting the side wall, light 3050entering the channel can be reduced to about 10% of its original powerafter a first reflection 3054, and subsequently be reduced to about 1%of its original power after a second reflection 3056. After two or morereflections, the stray light that reaches the image sensor, if any, cantypically comprise a very small amount of energy, thereby significantlyreducing the effect of stray light on the spectral resolution of inputlight.

The side walls of the plurality of channels may be configured to providesubstantially specular reflection of light from the side walls, forexample by providing polished side walls. Alternatively or incombination, side walls of the plurality of channels may be configuredto provide substantially diffusive reflection of light from the sidewalls, such that the reflected light may be scattered to manydirections.

Support Array Channels Comprising Bottom Wall with Central Opening

In the configurations shown in FIGS. 30A-30C, light entering the channelat an angle that is outside a predetermined range of allowable anglesmay be reflected one or more times from one or more side walls of thechannel, but in many cases can still exit from the channel at a lowintensity. The channel may be configured in a different way to preventat least some of the stray light from exiting the channel and travelingtowards the image sensor.

FIG. 31 illustrates a configuration of a support array channel 3100comprising a bottom wall 3105 having a central opening 3110. The channelmay comprise one or more side walls 3115 extending from a top end 3120of the channel to a bottom end 3125 of the channel. The bottom wall 3105can extend over the bottom end of the channel. The central opening 3110can have an area that is smaller than the cross-sectional area of thechannel at the bottom end. Light 3150 a entering the channel at a largeangle outside the predetermined range of allowable angles can hit aninternal surface of the bottom wall, such that the light is reflectedback away from the bottom end and does not exit the channel through thecentral opening. Alternatively, light 3150 b entering the channel at anangle outside the predetermined range can be reflected one or more timesfrom the side wall of the channel and subsequently exit the channelthrough the central opening of the bottom wall, or be reflected backfrom an internal surface of the bottom wall.

The performance characteristics of the channel comprising the bottomwall can depend on the ratio between the cross-sectional area of thechannel and the area of the central opening. Large ratios, correspondingto relatively larger areas of the bottom wall that can block lighttraveling towards the bottom end of the channel, can allow a smallerrange of angles of light to pass through the channel. In exemplaryconfigurations, the ratio between the cross-sectional area of thechannel and the area of the central opening can be in a range from about1.1 to about 1.5, in a range from about 1.2 to about 1.4, or about 1.3.In one exemplary configuration, a channel may have an internal diameterof about 576 um, and a center opening with a diameter of about 500 um,corresponding to a ratio of about 1.33 between the cross-section area ofthe channel and the area of the central opening. In some configurations,the cross-sectional area of the channel may be increased by reducing thethickness of the channel side walls.

Angle Limiting Layer

Alternatively to or in combination with one or more of theconfigurations discussed in reference to FIGS. 29A-31 , the spectrometermay further comprise an angle limiting layer configured to restrict theangles of light allowed to pass from the diffuser towards the filterarray.

FIG. 32A illustrates an exemplary configuration of an optical stack 3200comprising an angle limiting layer 3205. Optical stack 3200 comprises adiffuser 2805, filter array 2810, aperture array 2815, lens array 2820,support array 2825, and image sensor 2830 as described in reference toFIG. 28 . The optical stack 3200 further comprises the angle limitinglayer 3205, which may be disposed between the diffuser and the filterarray as shown in FIG. 32A. The angle limiting layer may be configuredin one of many ways to selectively allow light having an angle ofincidence within a predetermined range to pass through the layer.

FIG. 32B schematically illustrates an exemplary angle limiting layercomprising a micro-louver film 3210. The micro-louver film 3210, havinga thickness 3225, may comprise a plurality of light transmissivesections 3215 and a plurality of light blocking sections (“louvers”)3220, arranged alternatingly along a length of the micro-louver film.Adjacent light blocking sections or louvers may be separated by adistance 3230. The light transmissive sections can allow light to passtherethrough, while the light blocking sections can substantially absorbincident light. Light 3250 entering a light transmissive section of themicro-louver film at a large angle outside of the predetermined range ofallowable angles can hit a light blocking section before exiting themicro-louver film, wherein the majority of the light may be absorbed bythe light blocking section. Light 3252 entering a light transmissivesection at an angle within the predetermined allowable range can exitthe micro-louver film without hitting a light blocking section, therebypassing through to the filter array.

The maximum angle of incidence of light allowed to pass through themicro-louver film may be calculated using the following equation:

$\alpha = {\tan^{- 1}\frac{D}{T}}$wherein α is the maximum angle of incidence of light allowed to pass, Dis the distance between adjacent light blocking sections, and T is theeffective thickness of the micro-louver film, or the free-spacethickness divided by the index of refraction of the film. Thus, themaximum allowed angle of incidence may be controlled by adjusting one ormore of the thickness of the micro-louver film and the distance betweenadjacent light blocking sections. For example, to achieve a maximumallowed angle of incidence of 40°, assuming the light transmissivesections of the micro-louver film have an average index of refraction ofabout 1.3, the micro-louver film can be arranged to have a thickness ofabout 500 um, and a distance between adjacent light blocking sections ofabout 322 um. In many cases, the predetermined range for the angles ofincidence of input light allowed to pass through the micro-louver filmcan be from about −40° to about 40° with respect to the normal to theplane of the optical stack. Depending on the specific configuration ofthe optical stack, the predetermined range can be increased to a widerrange (e.g., from about −50° to about 50°), or decreased to narrowerrange (e.g., from about −30° to about 30°). An example of a commerciallyavailable micro-louver film suitable for incorporation with aspectrometer as described herein may be found on the Internet, forexample, at http://multimedia.3m.com/mws/media/793096O/3mtm-privacy-filter-alcf-p-abr0-film-data-sheet.pdf?fn=ALCF-P_ABR0_Control_Film_DS.pdf(3M Advanced Light Control Film).

FIG. 32C schematically illustrates another exemplary angle limitinglayer comprising a prism film 3240. The prims film may comprise an inputsurface 3242 configured to receive light from the diffuser 2805 and anoutput surface 3244 configured to output the light transmitted throughprism film. The output surface may comprise a plurality ofmicrostructures 3246, such as engineered microstructures on a polymericfilm. The plurality of microstructures may comprise a plurality ofpyramid shaped structures, as shown in FIG. 32C. The plurality ofmicrostructures can be configured to guide the light entering the prismfilm at large angles to exit from the film at a smaller angle span. Aslight 3250 that has entered the prism film at a large angle exitsthrough the microstructures, the angle of transmission of the outputlight can be modified by the microstructures, such that the output lightselectively comprises light having an angle of incidence within apredetermined range of acceptable angles (e.g., −40° to 40° with respectto the normal to the plane of the prism film). At least some of thelight that enters the prism film at an angle of incidence outside thepredetermined acceptable range may be redirected or reflected, enablingreuse of the light and thereby helping to improve the efficiency of thespectrometer. For example, as shown in FIG. 32C, light 3252 reaching asurface of a microstructure at a large angle may be redirected by themicrostructure into an adjacent microstructure. Light 3254 reaching asurface of a microstructure at a large angle may be reflected from themicrostructure surface back towards the diffuser 2805, wherein the lightmay be diffusively recycled and fed back into the prism film.

To control the maximum angle of incidence of light allowed to passthrough the prism film, one or more of the thickness of the film, theangle between adjacent microstructures, and the pitch of eachmicrostructure may be adjusted. For example, for a maximum angle ofincidence of about 35° with respect to the normal to the plane of theprism film, the prism film may be configured to have a thickness ofabout 62 um, an angle of about 90° between adjacent microstructures, anda pitch of about 24 um for each microstructure. To achieve betteruniformity, the pitch of each microstructure may be minimized. Anexample of a commercially available prism suitable for incorporationwith a spectrometer as described herein may be found on the Internet,for example, at http://multimedia.3m.com/mws/media/157408O/vikuiti-tm-t-bef.pdf?fn=T-BEF.pdf (3M Vikuiti™Thin Brightness Enhancement Film).

Control of Input Light Entering Spectrometer Module

In embodiments of the spectrometer comprising an integrated illuminationmodule, light generated by the illumination module and directed towardsthe sample is generally reflected back from the sample towards thespectrometer in a known, limited range of angles of reflection.Accordingly, light that reaches the spectrometer module or optical stackof the spectrometer at angles that are outside the known range of anglesof reflection for the illumination light may be assumed to haveoriginated from sources other than the illumination module (e.g.,ambient light, stray light), and may be prevented from entering theoptical stack in order to improve the spectral resolution of samplelight by the spectrometer. For example, an optical shading configured toblock the undesired angles of light may be incorporated into thespectrometer. Alternatively or additionally, a micro-louver film or aprism film as described herein may be incorporated into thespectrometer. For example, referring again to the spectrometer module160 shown in FIG. 7 , the angle-limiting film can be disposed betweenthe sample and the first diffuser 164, so as to limit the angles ofinput light that enter the optical stack. The angle-limiting film may beoriented such that the film maximally transmits the desired range ofangles. For example, in cases wherein the desired range of angles arenot centered about the normal to the spectrometer front face or plane ofthe optical stack, a special micro-louver film may be used in which thelouvers or light blocking sections are tilted at an angle thatsubstantially matches the angle of the axis about which the desiredrange of angles is centered.

The methods and apparatus disclosed herein can be incorporated withcomponents from spectrometers known in the art, such as spectrometersdescribed in U.S. Pat. Nos. 8,284,401, 7,236,243, U.S. Publication No.2015/0036138, U.S. Pat. No. 9,060,113, and U.S. Publication No.2014/0061486, the entire disclosures of which are incorporated herein byreference.

Although the detailed description contains many specifics, these shouldnot be construed as limiting the scope of the disclosure but merely asillustrating different examples and aspects of the present disclosure.It should be appreciated that the scope of the disclosure includes otherembodiments not discussed in detail above. Various other modifications,changes and variations which will be apparent to those skilled in theart may be made in the arrangement, operation and details of the methodand apparatus of the present disclosure provided herein withoutdeparting from the spirit and scope of the invention as describedherein.

While preferred embodiments of the present disclosure have been shownand described herein, it will be obvious to those skilled in the artthat such embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will be apparent to those skilledin the art without departing from the scope of the present disclosure.It should be understood that various alternatives to the embodiments ofthe present disclosure described herein may be employed withoutdeparting from the scope of the present invention. Therefore, the scopeof the present invention shall be defined solely by the scope of theappended claims and the equivalents thereof.

What is claimed is:
 1. An apparatus to measure spectra of a sample,comprising: a sensor comprising a detector and having a field of view tomeasure the spectra of the sample within the field of view; a filterarray, an aperture array, and a lens array, the filter array, theaperture array, and the lens array each being disposed between thesample and the detector; a diffuser disposed between the filter arrayand the sample; and a light source configured to direct an optical beamto the sample within the field of view, wherein the optical beamcomprises an aiming beam and a measurement beam, wherein the opticalbeam is configured to illuminate an area of the sample at leastpartially within the field of view of the detector, and wherein thefield of view of the detector is different than the area of the sampleilluminated by the optical beam such that the spectra of the sample aredefined by at most a portion of the area of the sample within thedetector's field of view.
 2. The apparatus of claim 1, wherein theaiming beam is configured to reflect from the sample to be visible to auser of the apparatus.
 3. The apparatus of claim 1, wherein the aimingbeam and the measurement beam are configured to overlap on the sample.4. The apparatus of claim 1, wherein the aiming beam and the measurementbeam are configured to illuminate substantially similar areas of thesample.
 5. The apparatus of claim 1, wherein the aiming beam and themeasurement beam comprise offset optical axes, and wherein the aimingbeam and the measurement beam are configured to converge at a defineddistance from the apparatus.
 6. The apparatus of claim 1, wherein theaiming beam and the measurement beam are transmitted along a commonoptical axis.
 7. The apparatus of claim 1, wherein the aiming beam andthe measurement beam are produced by the same light source.
 8. Theapparatus of claim 1, wherein the area of the sample illuminated by theoptical beam partially overlaps the area of the sample within the fieldof view of the detector.
 9. The apparatus of claim 1, wherein the areaof the sample illuminated by the optical beam is smaller than the areaof the sample within the field of view of the detector.
 10. Theapparatus of claim 9, wherein the area of the sample illuminated by theoptical beam is substantially within the field of view of the detector.11. The apparatus of claim 1, wherein the field of view of the detectoris at least 90 degrees.
 12. The apparatus of claim 1, wherein the filterarray is configured to transmit light through a plurality of opticalchannels leading to the detector.
 13. The apparatus of claim 12, whereinthe plurality of optical channels comprises overlapping fields of viewwhich at least partially define the field of view of the detector. 14.The apparatus of claim 1, wherein the measurement beam comprisesmodulated light, and wherein the apparatus is configured to demodulatethe modulated light.
 15. The apparatus of claim 14, wherein theapparatus is configured to distinguish the modulated light from ambientlight.
 16. The apparatus of claim 1, wherein the apparatus is configuredto transmit the measurement beam to the detector and inhibittransmission of the aiming beam to the detector.
 17. An apparatus tomeasure spectra of a sample, comprising: a sensor comprising a detectorand having a field of view to measure the spectra of the sample withinthe field of view; and a light source configured to direct an opticalbeam to the sample within the field of view, wherein the optical beamcomprises an aiming beam and a measurement beam, wherein the opticalbeam is configured to illuminate an area of the sample at leastpartially within the field of view of the detector, wherein the field ofview of the detector is different than the area of the sampleilluminated by the optical beam such that the spectra of the sample aredefined by at most a portion of the area of the sample within thedetector's field of view, wherein the measurement beam comprisesmodulated light, and wherein the apparatus is configured to demodulatethe modulated light, and wherein the apparatus is configured todistinguish the modulated light from the aiming beam.